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Iris identification post-mortem avec utilisation en police scientifique - Forenseek

Post-Mortem Iris Identification

News,

For a long time, the iris was thought to become unusable almost as soon as a person died. Several recent studies show the opposite, and the most comprehensive of them has just been published in the United States.

The iris is the coloured ring that surrounds the pupil. Its relief, made up of crypts, furrows and striations, forms a texture that belongs to one individual alone and becomes fixed in early childhood, never changing afterwards. A high-resolution photograph is enough to capture it, after which an algorithm encodes it into a template unique to that person and compares it against every record already held in a database. In France, iris biometrics remains very little used, yet for years it has supported the identification of living individuals elsewhere in the world. In the United States, the FBI has turned it into a service in its own right, the NGI Iris Service, fed by a national network in which sheriffs enrol the iris of suspects and convicted offenders at the time of booking. One question nonetheless remained open, one that almost no one had seriously examined. What becomes of this identifier once the person has died?

A certainty that science eventually overturned

When death occurs, the pupil becomes fixed, most often wide open, and the cornea is gradually veiled by a whitish film, the milky sheen sometimes seen in the gaze of the dead. As early as 2001, John Daugman, the British engineer behind automated iris recognition, told the BBC that this twofold change made the task considerably harder. The notion took firm hold, to the point of feeding the claim, repeated as though self-evident, that the iris became unusable within minutes.

The past 15 years have patiently dismantled that certainty, one study after another [3]. As early as 2016, it was established that an iris could still be recognised several days after death [3]. How the body is preserved soon proved to be the decisive factor. Left outdoors, the iris degrades quickly, whereas fingerprints and the face withstand decomposition far better, as Bolme and colleagues observed [3]. At the other extreme, Sauerwein and colleagues recovered irises that were perfectly analysable 34 days after death, on bodies left outdoors but exposed to the cold of winter [3]. The first studies genuinely tracked over time, carried out in Warsaw by Mateusz Trokielewicz and colleagues, reached a conclusion that few specialists had anticipated. Under favourable conditions, the iris can be analysed without notable difficulty 5 to 7 hours after death, and identification sometimes remains possible up to 3 weeks afterwards [4].

The most comprehensive study to date

The most accomplished demonstration is very recent. It comes from a large team bringing together the University of Notre Dame and Michigan State University, led by Rasel Ahmed Bhuiyan, and it has been accepted by a leading biometrics journal [1]. The researchers first assembled an image collection without precedent, more than 10,000 iris photographs gathered from 259 deceased subjects, in visible light as well as near-infrared, the wavelength that best reveals the texture of the iris [1]. For some of them, the interval between death and image capture reached 1,674 hours, close to 70 days [1].

The corpus includes a case never before published, that of a person whose eye was photographed both before and after death, which made it possible to compare the iris of the living individual directly with that of the deceased [1]. It also contains atypical configurations, rarely documented until then, such as an eye dislodged from its orbit by an injury [1]. Adding the few collections already available, the team brought together images of 338 deceased subjects, the largest sample ever assembled on the subject, then ran them through 5 recognition systems, from the oldest to the most recent, some based on artificial intelligence and others already on the market [1]. The results confirm and refine what the literature had hinted at. When the body has been kept in good conditions, current systems still recognise the iris several hours, sometimes several days, after death [1]. Here again, everything hinges on preservation, and the gap can be considerable. A body left in a field at the height of summer will see its iris degrade within a few days, until any comparison becomes impossible. The same body placed in a refrigerated mortuary drawer at a medico-legal institute, at around 6 degrees Celsius, keeps a usable iris for several weeks [1].

For an investigator, a magistrate or a forensic pathologist, the consequence is clear. No fixed deadline marks the moment when the iris would cease to be identifiable. There are only more or less favourable conditions, which will have to be reconstructed and documented in each case.

The study does not stop at measuring performance. It also delivers an open-source software tool, named PMExpert, designed to support the examiner and already in use since 2021 within a United States medico-legal institute [1]. Rather than returning a definitive ‘yes’ or ‘no’, it highlights the regions of the iris on which it relies to match two images, ante-mortem and post-mortem, leaving the expert free to verify and weigh the correspondence [1]. The software and the accompanying data are made available to forensic services free of charge, through the public United States criminal justice data archive [1].

Estimating how long a person has been dead

The same images fed a second piece of research, one that must be carefully distinguished from the first [2]. This one no longer seeks to identify an individual from the iris, but to estimate how long that individual has been dead. Conducted by Rasel Ahmed Bhuiyan and Adam Czajka and presented at the WACV 2025 conference, it draws on European collections and on the new dataset, 348 subjects in all [2]. The principle is nothing new. For centuries, the forensic pathologist has estimated the post-mortem interval from the positive signs of death that evolve at a relatively steady pace, such as algor mortis, the onset of livor mortis, or the appearance and then the disappearance of rigor mortis. What is new lies in the sign chosen and in the way it is read.

Here, what the machine observes is the white veil that gradually spreads across the eye after death. The more advanced it is, the longer ago death occurred. The researchers trained a deep learning model to perform this reading from the iris photograph alone [2]. Accuracy depends, once again, on environmental factors. In the scenario closest to real conditions, when the model must rule on bodies and settings it has never encountered, it is off by an average of about 3 days [2]. It can therefore point to a window, but never to a precise hour. Feasibility is established, yet we remain far from a fully reliable tool for dating death [2].

For the courts, a lead to handle with caution

In practical terms, what use is this in an investigation? Faced with an unidentified body, the eye is photographed, the software proposes a list of possible matches from a database, and an expert then confirms or rules out each of them [1]. The iris will replace neither DNA, nor fingerprints, nor forensic odontology, the three primary identifiers used to formally identify a body. It is an addition to them, above all when those methods take time or prove unusable, for want of ante-mortem data, on bodies that are too degraded or fragmented.

Its main advantage is speed. Comparing the iris of an eye against a biometric database takes only a few seconds, an argument that can weigh heavily when many victims must be identified under time pressure, after a mass-casualty event for example. This ability to reliably identify someone after death nonetheless raises a security concern of the first order. If the iris of a deceased person remains identifiable, one can imagine that a deliberately removed eye, or even a stored image, might be used to unlock a phone or to clear a biometric checkpoint based on this method. The authors anticipated this scenario and adapted software designed to flag fake eyes, a form of presentation attack detection, showing that it very quickly learns to recognise a deceased person’s iris and reject it [1].

Conclusion

The real reach of this advance remains to be measured. The window of opportunity exists, but it closes quickly, as the corneal veil thickens and the tissues decompose. The images needed to train and test the software remain scarce and hard to gather, something the researchers themselves acknowledge as a major obstacle [1]. And no framework yet defines what would make such an identification admissible in court. As long as that framework is missing, the iris of a deceased person is to be weighed like any other expert finding, with its conditions to document and its share of debate.

One obvious point deserves to be stressed above all. Identifying someone from the iris presupposes that this iris is already on file, recorded while the person was alive, when applying for a biometric passport in countries that provide for it, or when gaining access to a secure site through iris recognition. Without that reference, even the most powerful analysis leads nowhere. In France, where the iris feeds no identification file, the technique is therefore, for now, a matter of horizon-scanning more than routine practice. It nonetheless deserves close attention, for it illustrates a deeper trend, that of a forensic science learning to make the body speak when DNA and fingerprints fall silent.

References

  • [1] Bhuiyan R. A., Farmanifard P., Sharma R., Kuehlkamp A., Boyd A., Flynn P. J., Bowyer K. W., Ross A., Chute D., Czajka A. (2026). Beyond Mortality, Advancements in Post-Mortem Iris Recognition through Data Collection and Computer-Aided Forensic Examination. IEEE Transactions on Biometrics, Behavior, and Identity Science, early access. arXiv:2603.26976. https://ieeexplore.ieee.org/document/11063436
  • [2] Bhuiyan R. A., Czajka A. (2025). Forensic Iris Image-Based Post-Mortem Interval Estimation. IEEE/CVF Winter Conference on Applications of Computer Vision, WACV 2025. arXiv:2404.10172.
  • [3] Boyd A., Yadav S., Swearingen T., Kuehlkamp A., Trokielewicz M., Benjamin E., Maciejewicz P., Chute D., Ross A., Flynn P., Bowyer K., Czajka A. (2020). Post-Mortem Iris Recognition, A Survey and Assessment of the State of the Art. IEEE Access, vol. 8, p. 136570-136593.
  • [4] Trokielewicz M., Maciejewicz P., Czajka A. (2024). Post-mortem Iris Biometrics, Field, Applications and Methods. Forensic Science International.

Analyse ADN laboratoire police scientifique transfert

When an absent investigator’s DNA turns up on a sealed exhibit

Forensic police, News,

A case that had gone unsolved for eighteen years is reopened. From a plastic bag kept as a sealed exhibit, analysts obtain a full DNA profile. Run against the staff elimination database, it returns a name, that of an investigator. The trouble is that this investigator was eighty kilometres from the laboratory and had never set foot at the scene or in the exhibit storage room. The profile was nonetheless his. DNA had identified a person with near-certainty on an item he had never handled. Reported in early 2026 by Gao et al. in Forensic Science International: Genetics, this case is a reminder of a distinction that is too often overlooked: knowing whose DNA a sample carries and knowing how it got there are two different questions.

Identifying the source is not explaining the activity

The forensic laboratory’s result answered one question perfectly, the origin of the genetic material, but it offered no reliable information about the circumstances of deposition. This distinction has long shaped the reasoning of forensic geneticists. In 1998, Cook, Evett et al. [1], writing in Science & Justice, proposed a hierarchy of propositions setting out three levels of interpretation, running from the source to the offence itself. The sub-source level, specific to DNA, was added later, notably by Evett et al. in 2002 [2]. Establishing whose biological profile a sample matches sits at the very bottom of this ladder. Explaining how that profile came to be there, on a substrate or at a crime scene, belongs to the activity level, which is higher and far harder to establish. For a judge, the distinction is decisive. A laboratory can state with great confidence that the DNA profile obtained from a biological sample matches an individual’s profile, yet cannot say, with the same assurance, what that presence means.

The four levels of interpretation: a textbook case

The classic Cook and Evett example, a sexual assault case, where each level adds a further layer of inference on top of the one below:

  • Sub-source level:
    “The DNA in the sample comes from the suspect” (rather than from an unknown person). This is what the raw DNA comparison measures directly. It speaks only to DNA, nothing more.
  • Source level:
    “The semen comes from the suspect.” This adds identification of the body fluid, provided it has been established that the stain really is semen.
  • Activity level:
    “The suspect had sexual intercourse with the complainant.” This adds the mechanism of deposition where transfer, persistence and contamination come into play.
  • Offence level:
    “The suspect raped the complainant.” This adds the absence of consent which the expert cannot decide, since that is for the court.

At each step up, science can say a little less, and the weight of the evidence diminishes.

How more sensitive methods changed the picture

The problem is not new, but it has changed in scale as DNA analysis has advanced. Today’s kits can recover usable DNA profiles from just a few cells, where once a far larger amount of DNA was needed. In 1997, van Oorschot and Jones [9] showed that mere contact is enough to deposit DNA. Since then, the literature has documented many routes of transfer, both direct and indirect, surveyed in van Oorschot et al.’s 2019 review [10]. The effect cuts both ways. The very sensitivity that makes it possible to reopen old cases also raises the chance of detecting a DNA profile unrelated to the events in question. Studies remain cautious about frequencies, which vary widely with conditions, so much so that some authors regard secondary transfer as an uncommon event. Generalisation must therefore be handled with care, in both directions.

The risk of DNA transfer in evidence handling

The journey of a sealed exhibit, from the crime scene to the laboratory bench, passes through a series of handling steps during which DNA can move. The packaging of the item itself plays a part. Stella et al. [7] showed in 2026 that this transfer can run two ways: DNA deposited on an item may migrate to the inner surface of the packaging, so that the sought-after profile is missing from the analysis; or it may transfer to another area of the item, where it has no business being and clouds interpretation. Goray et al. [6] noted in 2019 that the outer surface of gloves could carry, alongside the target profile, that of the examiners themselves, particularly when opening and resealing the packaging. It is precisely this risk that the examination protocols used by forensic services are designed to head off, requiring decontaminated gloves changed for each new item. Examination tools pose a comparable problem, described as early as 2015 by Szkuta et al. [8]. That an investigator might contaminate an item or surface after the fact is therefore no far-fetched hypothesis; Fonneløp’s team [3,4] has studied the phenomenon right down to evidence bags themselves.

To explain the presence of this profile on an exhibit the investigator had never come near, Gao et al. [5] rule out item-to-item transfer in favour of a likely airborne route: the DNA is thought to have settled on a colleague’s clothing before detaching as that colleague approached the sample pre-treatment area. Without the staff elimination database, this hypothesis would never have come to light.

What this distinction changes for the evaluation of evidence

For legal professionals, the lesson of this case is not that DNA is unreliable, but rather that a solid genetic identification at the source level can coexist with a fragile explanation at the activity level. The whole risk lies in sliding from one to the other, when the strength of the former colours the assessment of the latter. To guard against this slide, some forensic geneticists argue that the expert should reason explicitly at the activity level and set out the scenarios consistent with the observations. This is notably the position of the School of Criminal Justice at the University of Lausanne and of the European guideline on evaluative reporting [11].

Conclusion :

The case of the investigator who was never at the scene illustrates the stakes better than any theoretical reminder could. His DNA profile, entirely genuine, sat on a sealed exhibit he had never touched, in a case whose scene he had never visited. Without a safeguard that brought another explanation to light, this finding could have been read as a genuine investigative lead backed by a “relevant” DNA profile. A genetic result is worth not only what it identifies, but what it reasonably allows one to infer, and that is never settled on a single trace alone. A DNA profile must be weighed within the wider body of evidence, never in isolation.

References :

  • [1] Cook R., Evett I.W., Jackson G., Jones P.J., Lambert J.A. (1998). A hierarchy of propositions: deciding which level to address in casework. Science & Justice, 38(4), 231-239.
  • [2] Evett I.W., Gill P.D., Jackson G., Whitaker J., Champod C. (2002). Interpreting small quantities of DNA: the hierarchy of propositions and the use of Bayesian networks. Journal of Forensic Sciences, 47(3), 520-530.
  • [3] Fonneløp A.E., Egeland T., Gill P. (2015). Secondary and subsequent DNA transfer during criminal investigation. Forensic Science International: Genetics, 17, 155-162.
  • [4] Fonneløp A.E., Johannessen H., Egeland T., Gill P. (2016). Contamination during criminal investigation: Detecting police contamination and secondary DNA transfer from evidence bags. Forensic Science International: Genetics, 23, 121-129.
  • [5] Gao L. et al. (2026). A rare and atypical case of long-distance indirect DNA transfer: Contamination from an investigator never present at the scene. Forensic Science International: Genetics.
  • [6] Goray M., Pirie E., van Oorschot R.A.H. (2019). DNA transfer: DNA acquired by gloves during casework examinations. Forensic Science International: Genetics, 38, 167-174.
  • [7] Stella C.J., Goray M., Meakin G.E., van Oorschot R.A.H. (2026). DNA transfer in packaging: Investigation of mitigation strategies. Journal of Forensic Sciences, 71(1), 197-210.
  • [8] Szkuta B., Harvey M.L., Ballantyne K.N., van Oorschot R.A.H. (2015). DNA transfer by examination tools, a risk for forensic casework? Forensic Science International: Genetics, 16, 246-254.
  • [9] van Oorschot R.A.H., Jones M.K. (1997). DNA fingerprints from fingerprints. Nature, 387, 767.
  • [10] van Oorschot R.A.H., Szkuta B., Meakin G.E., Kokshoorn B., Goray M. (2019). DNA transfer in forensic science: A review. Forensic Science International: Genetics, 38, 140-166.
  • [11] ENFSI, Guideline for Evaluative Reporting in Forensic Science, 2015

arnaques sentimentales brad pitt enquête forenseek police scientifique

How do romance scams work?

Articles, Justice, News,

A recent case involving a French woman defrauded of several hundred thousand euros by an individual impersonating Brad Pitt has received widespread media attention. The perpetrator relied on prolonged exchanges, personalized content, and manipulated visual materials to sustain a credible relationship over several months. While this case has drawn public attention, it reflects a well-documented broader trend. According to the Federal Trade Commission, losses related to romance scams exceeded 1.1 billion dollars in 2023, with a steady increase in recent years. Research by Whitty and Buchanan (2022), published in Crime Science, further shows that these frauds affect an increasingly diverse range of victims, far beyond common stereotypes.

Understanding the effectiveness of romance scams

Romance scams rely on robust psychological mechanisms that have been widely studied in criminology and social psychology. Their effectiveness does not stem from individual vulnerability, but from a gradual construction process. The interaction often begins in a mundane way before evolving into a personalized and coherent relationship. The offender adapts their discourse, adjusts response timing, introduces credible biographical elements, and progressively establishes a climate of trust.

This process is based on a gradual commitment of the victim to the relationship, a narrative coherence that reduces the perception of inconsistencies, the mobilization of emotions such as attachment, concern, and urgency, and the emergence of cognitive dissonance when initial doubts arise.

The turning point: cognitive dissonance

Cognitive dissonance represents a critical stage, and likely one of the most decisive mechanisms in the persistence of the fraud. It reflects an internal tension between two incompatible realities: on one side, an emotionally invested relationship, and on the other, the possibility of deception. Acknowledging the scam involves far more than a rational reassessment. It means admitting an error, often financially costly, but above all emotionally significant.

At this stage, several barriers emerge. Feelings of guilt, the realization of having been manipulated, fear of judgment or misunderstanding from relatives, and the perception of having reached a point of no return all contribute to maintaining the relationship. This is compounded by a form of abrupt disillusionment that can be psychologically difficult to process.

In this context, continuing the interaction may paradoxically serve as a way to preserve internal consistency and avoid a significant emotional shock. It is precisely at this moment that disengagement becomes the most difficult, even though warning signs are the most evident. As the relationship progresses, decisions are no longer evaluated purely on a rational basis. They are embedded in an already invested relational framework, which explains why informed and socially integrated individuals can also become victims.

From interaction to trace

From a forensic perspective, these cases generate specific types of traces. Unlike traditional material evidence, the available elements consist primarily of digital interactions.

Written messages, audio recordings, images, and videos form a dataset that documents not only events but also an interaction. These elements allow for the analysis of the offender’s discourse structure, the rhythm of solicitations, the turning points leading to financial requests, and the strategies used to adapt to the victim’s reactions. The introduction of manipulated content, particularly through deepfake techniques, further complicates this analysis. Such materials enhance perceived credibility without constituting direct proof of identity. In practice, meaning does not emerge from isolated elements, but from how they connect and unfold over time.

Objectives and constraints of the investigation

Investigations into romance scams pursue several simultaneous objectives.

  • The first concerns financial flows, with the aim of tracing transactions, identifying intermediary accounts, and, where possible, initiating asset recovery procedures.
  • The second focuses on identifying the perpetrators. In many cases, these scams involve organized networks, with a division of roles between profile creators, conversation operators, and financial intermediaries.
  • The third objective is to understand the modus operandi in order to support prevention efforts and improve detection capabilities.

These investigations are made particularly complex by several factors, including geographical fragmentation, the use of multiple identities, and reliance on dispersed technical infrastructures.

The central challenge of interpretation

One of the main challenges lies in interpreting the exchanges. Like any trace, digital communications only make sense within their context. A message cannot be understood independently of the relationship in which it occurs. It reflects not only the offender’s actions but also how the victim responds under the influence of manipulation. This requires a particularly rigorous analytical approach. The analysis must account for the chronology of interactions, the emotional context, identifiable manipulation strategies, and corroborating external elements. Without this contextualization, the risk of misinterpretation remains significant.

Towards a forensic science of interaction ?

These cases illustrate a broader evolution in the types of traces used in forensic science. Alongside traditional material and digital evidence, interactional traces are emerging, generated through technology-mediated relationships. Deepfakes, fake profiles, and scripted conversations do not represent a fundamental rupture. They extend existing manipulation strategies while increasing their credibility and scalability. The challenge for forensic science lies in integrating these new forms of traces into robust methodological frameworks capable of combining technical data with behavioral analysis.

Judicial challenges and perspectives

For legal practitioners, these cases raise specific issues. The legal qualification of the facts, the assessment of victim consent, and the evidentiary value of exchanges require a nuanced approach.

A first obstacle lies in underreporting. Victims still rarely file complaints, often due to shame, guilt, or fear of judgment. Data from the Federal Bureau of Investigation indicate that reported losses represent only a fraction of the actual phenomenon. Even when cases are reported, proceedings rarely lead to successful prosecutions. The transnational nature of these crimes, the use of fictitious identities, and the complexity of financial flows significantly limit both prosecutions and convictions.

Although data are abundant, their interpretation requires particular rigor. The objective is not to accumulate evidence, but to produce a coherent and scientifically grounded analysis. These developments call for stronger collaboration between investigators, analysts, and behavioral science experts in order to better address offences where evidence lies as much in interaction as in technical data.

Sources

Federal Trade Commission (2024). Consumer Sentinel Network Data Book 2023 – Romance scam losses. Available online:https://www.ftc.gov/reports/consumer-sentinel-network-data-book-2023

Whitty, M. T., & Buchanan, T. (2022). The online romance scam: Causes and consequences. Crime Science. Available online: https://crimesciencejournal.biomedcentral.com/articles/10.1186/s40163-022-00166-2

France Bleu (2025). Retour sur l’arnaque au faux Brad Pitt qui a coûté 830 000 euros à une internaute française. Available online: https://www.francebleu.fr/infos/faits-divers-justice/retour-sur-l-arnaque-au-faux-brad-pitt-qui-a-coute-830-000-euros-a-une-internaute-francaise-9633205

Le Monde (2025). Qui se cache derrière les arnaques sentimentales qui se multiplient en France ?
Available online: https://www.lemonde.fr

Federal Bureau of Investigation (2024). Internet Crime Report – Romance scams.
Available online: https://www.ic3.gov/Media/PDF/AnnualReport/2023_IC3Report.pdf

Can human activity be reconstructed from a smartphone ?

News, Unclassified, ,

A recent study conducted by researchers at the Netherlands Forensic Institute and the University of Amsterdam examines whether data generated by smartphone sensors can be meaningfully exploited in a judicial context. The central question is whether motion signals recorded by these devices can be translated into a probabilistic evaluation capable of assessing whether a specific human activity occurred at a particular point in time. As everyday objects increasingly capture fine-grained behavioral traces, the methodological integration of such data into judicial reasoning has become a critical issue.

Understanding Human Activity Recognition

Human Activity Recognition, commonly referred to as HAR, is a research field that has developed over the past decade, initially within connected health, sports tracking, and smart device applications. Its principle is to use embedded smartphone sensors to identify categories of movement based on numerical signals. Most smartphones are equipped with an accelerometer and a gyroscope that continuously record variations in movement and orientation. From these time series, statistical models trained on known activities learn to recognize characteristic patterns. Walking, running, and periods of inactivity generate distinct signatures that the algorithm can compare with data extracted from a phone under examination.

In everyday use, this classification supports functions such as physical activity tracking or fall detection. In a judicial setting, however, the objective is narrower and more demanding. The issue is not simply to label a movement, but to determine what these recordings can reasonably support regarding a specific activity, and what they cannot establish.

From classification to probabilistic evaluation

In forensic science, the task is not to assert that an event occurred, but to assess the strength with which observed data support one hypothesis over an alternative. Outputs from activity recognition models can be incorporated into this framework by expressing their evidential value in the form of a likelihood ratio. In practical terms, this involves evaluating whether the recorded sequence is more probable under one clearly defined scenario than under another. The algorithm does not decide that a person was running or walking. It provides a comparative measure of how strongly the data support one of the competing hypotheses.

Methodological illustration in a judicial context

Consider a smartphone seized in the course of an assault investigation. At a time considered critical to the events, the motion sensors recorded a sequence of data.

Two hypotheses are formulated. Under the first, the individual was walking normally. Under the second, the individual was running. The analysis indicates that the observed signals are ten times more probable under the running hypothesis than under the walking hypothesis. The likelihood ratio is therefore ten in favor of the proposition that the person was running. This result does not constitute direct proof of running. It expresses the relative probabilistic support that the data provide for that hypothesis compared with the alternative. The evidential weight of this information within the case file will depend on the remaining evidence and on the overall coherence of the competing scenarios.

The principal advantage of this approach lies in its compatibility with the Bayesian logic already recognized in the evaluation of scientific evidence.

Scientific and methodological limitations

Human Activity Recognition models are typically trained on datasets collected under controlled conditions. In real-world situations, however, numerous factors influence the recorded signal. The way the phone is carried, whether in a pocket, a bag, or held in the hand, the nature of the ground surface, the individual’s emotional state, and the device’s software configuration may all affect the measurements. Acute stress, for example, can alter the amplitude and regularity of movements. Similarly, a software update may modify the sampling frequency or the filtering parameters applied to sensor data. These technical aspects, often invisible to users, directly shape the structure of the data being analyzed.

Inter-individual variability must also be considered. Two individuals running at comparable speeds may nevertheless produce slightly different motion signatures.

In addition, data integrity must be verified. Sensor logs may be incomplete, altered, or disabled depending on device settings. As with any algorithmic method, independent validation, knowledge of error rates, and transparency regarding the model used are essential prerequisites for admissibility in a judicial context.

From source to activity, a parallel with Forensic Genetics

These findings echo a distinction that has become central in forensic genetics, namely the difference between the source level and the activity level.

In our article “Cigarette Butts: Can a Simple Kiss Distort DNA Interpretation?”, we emphasized that identifying the origin of a genetic profile does not, by itself, explain how it was deposited. The same reasoning applies here. Demonstrating that a motion pattern is compatible with running does not, on its own, establish the precise circumstances of the action. In both contexts, the key issue is identical. Moving from a technical observation to an interpretation at the activity level requires explicit scenario comparison and rigorous probabilistic evaluation. Data extracted from a smartphone, like DNA profile data, acquire meaning only within this structured analytical framework.

For judges and forensic experts, the primary challenge lies less in the technology itself than in understanding its methodological foundations. Producing a likelihood ratio requires clearly defined competing hypotheses, documented model validation, and explicit acknowledgment of analytical limitations. A smartphone does not become an automatic witness to events. Under strict conditions, however, it may provide probabilistic information capable of informing one scenario among several. The central issue is therefore not the mere availability of digital data, but the scientific robustness and legal relevance of their interpretation.

Source :

McCarthy, C., van Zandwijk, J. P., Worring, M., & Geradts, Z. (2025). Forensic Activity Classification Using Digital Traces from iPhones: A Machine Learning-based Approach.
Disponible en ligne : https://arxiv.org/abs/2512.03786

Quand un baiser permet de transférer l'ADN d'une tierce personne sur un mégot de cigarette. Forenseek

Cigarette butts: can a simple kiss mislead DNA interpretation?

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A classic crime scene issue

Cigarette butts represent a major biological substrate in forensic casework. Rich in epithelial cells deposited through saliva, they generally yield exploitable genetic profiles. In practice, the discovery of a DNA mixture on a cigarette filter is often interpreted as evidence that two individuals smoked the same cigarette or handled it in close succession. However, with the increasing sensitivity of modern quantification and STR amplification techniques, laboratories are now capable of detecting minute amounts of DNA, including those resulting from indirect transfers. The question is therefore no longer simply “Whose profile is this?”, but rather “How did this DNA get there?”

An experimental protocol based on two realistic scenarios

The authors of this pilot study tested two distinct configurations.

First scenario: kiss, then cigarette.
A couple exchanged a deep kiss involving saliva transfer. Each partner then smoked a cigarette at different intervals: immediately, and then 5, 15, 30, 60, 90, and 120 minutes after contact. The objective was to assess whether the partner’s DNA, retained in the oral cavity, could be secondarily transferred onto the cigarette filter.

Second scenario: shared cigarette.
Both partners alternately smoked the same cigarette, reproducing a case of direct co-consumption. Samples were analyzed either immediately after collection or after a 30-day storage period in order to evaluate the impact of time on DNA quantity and quality.

Detectable persistence for up to two hours

In the “kiss then cigarette” scenario, alleles attributable to the non-smoking partner were detected on cigarette butts up to 120 minutes after contact. The quantity of transferred DNA gradually decreased over time but remained detectable under several experimental conditions. In other words, the presence of a minor DNA profile on a cigarette butt does not, by itself, demonstrate that two individuals smoked the cigarette. A prior intimate contact could be sufficient to explain the mixture. These findings align with previous research showing that salivary DNA can persist in the oral cavity for several tens of minutes, or longer, depending on individual and physiological factors.

The determining effect of processing delay

The study also demonstrated a significant decrease in total DNA quantity after 30 days of storage, accompanied by an increase in the degradation index. This phenomenon particularly affects the minor component of the mixture, which is more fragile and more prone to partial loss (allelic drop-out, imbalance). In practical terms, a cigarette butt analyzed promptly may reveal a detectable mixture, whereas delayed processing could result in an apparently single-source profile.

Such temporal variability complicates interpretation and underscores the importance of carefully documenting storage conditions and processing timelines.

The contribution and limits of Y-STR markers

In cases where the female partner smoked after the kiss, Y-STR analyses allowed specific monitoring of the transferred male component. Complete Y profiles were obtained up to one hour after contact, with alleles still detectable at two hours under certain conditions. However, progressive degradation and low template quantities again require caution and contextual interpretation.

Interpreting at the activity level is essential

These findings clearly illustrate the now central distinction between:

  • Source level: whose DNA is it?
  • Activity level: by what mechanism was it deposited?

When a mixture is detected on a cigarette butt recovered from a crime scene, several scientifically plausible scenarios may exist: co-consumption, successive handling, secondary transfer following prior intimate contact, or even a combination of these hypotheses. An expert cannot therefore limit their assessment to identifying the DNA contributors. They must also evaluate deposition mechanisms consistent with current scientific knowledge, taking into account secondary transfer dynamics and the impact of time.

Conclusion

This experimental study, conducted under controlled conditions, does not claim to establish a universal rule applicable to all judicial situations. It does, however, clearly demonstrate that secondary oral transfer onto a cigarette butt is possible and may remain detectable for up to two hours after a simple kiss. At a time when the sensitivity of genetic analysis techniques continues to increase, these results reaffirm a fundamental principle of forensic science: detecting DNA is not, in itself, proof of a particular scenario. Interpretation must be rigorous, contextualized, and grounded in activity-level reasoning in order to avoid overinterpretation before the courts..

Source :

GIANFREDA, Denise, CORRADINI, Beatrice, FERRI, Gianmarco, FERRARI, Francesca, BORCIANI, Ilaria, CECCHI, Rossana, SANTUNIONE, Anna Laura. Preliminary study of mixed traces on cigarette butts and non-self DNA transfer, persistence, prevalence and recovery in different forensic scenarios. Legal Medicine, 2026, vol. 81, article 102803. DOI: 10.1016/j.legalmed.2026.102803.

When a medicine becomes a trafficked product

News,

Pregabalin is a well-known medicinal product. Prescribed in particular for epilepsy and certain neuropathic pain conditions, it circulates legally within a strictly regulated framework. Yet the recent increase in seizures in France shows that it can also enter illicit resale networks. This situation raises a central question in judicial investigations: how can it be demonstrated that a legally marketed pharmaceutical product has been diverted from its therapeutic use? Unlike classically prohibited narcotics, the issue here is not the existence of the molecule itself. Pregabalin is authorised, documented, and readily identifiable by forensic laboratories. The challenge therefore lies not merely in determining the substance involved, but in establishing whether it is being used within a lawful framework.

Identifying the molecule

From an analytical standpoint, laboratories rely on well-established methods to identify pregabalin and verify its composition. Chromatographic techniques coupled with mass spectrometry make it possible to confirm the nature of the molecule present, assess its purity, and detect potential modifications, such as admixture with other substances. This step remains essential. It allows investigators to rule out counterfeiting or product alteration and to objectively establish the actual composition of the seized material. In some cases, the presence of additional psychoactive substances or formulation irregularities may constitute a significant element of the investigation. However, chemical identification alone is not sufficient to demonstrate diversion.

Inconsistency between medical use and observed circumstances

The demonstration of diversion often relies on a discrepancy between the expected therapeutic use and the concrete circumstances of the seizure. Very large quantities, repackaging into small bags, the absence of a prescription, or the presence of substantial amounts of cash may all suggest an intent to resell. In forensic science, no conclusion can rest on a single isolated element; taken individually, these indicators are insufficient to establish an offence. It is their convergence that supports the hypothesis of organised illicit trafficking.

Toward pharmaceutical traceability

Medicinal products are not anonymous items. They carry batch numbers and form part of a regulated distribution chain. The analysis of these elements may reveal that a batch has left the pharmaceutical supply chain irregularly, has been stolen or diverted during distribution, or originates from a supply route different from that authorised in France. This work also addresses a further essential question: is the product authentic, or is it counterfeit? Examination of packaging, printing, composition, and physicochemical characteristics may reveal inconsistencies incompatible with regulated manufacturing. The distinction is decisive, as an authentic medicine resold unlawfully and a counterfeit product do not fall under the same criminal offences or carry the same penalties. Comparative analysis of seized batches may also reveal similarities across different cases, suggesting a common source of supply or the existence of a structured organisation.

In this type of case, the forensic laboratory does not merely confirm the presence of a molecule. The analyses performed provide technical elements relevant to the investigation, such as the exact composition of the product, the nature of cutting agents, potential modifications, or anomalies capable of guiding further inquiries. These findings are subsequently assessed alongside investigative information—quantities seized, conditions of possession, supply routes—in order to clarify the legal qualification of the facts. Identification of the substance thus remains an essential step. However, the interpretation of analytical results also contributes to determining whether the product is consistent with legitimate therapeutic use or part of an illicit resale scheme.

A phenomenon that is not isolated

Pregabalin is not an isolated case. Other medicines have already illustrated this permeability between therapeutic use and illicit trafficking. Fentanyl, a highly potent synthetic opioid used in anaesthesia and in the management of severe pain, has been subject to large-scale diversion in several countries, with major public health consequences. In France, prolonged-release morphine marketed under the brand name Skénan® has also been involved in non-medical uses, notably through injection following extraction of the active substance.

These examples demonstrate that pharmaceutical diversion does not depend on an “exotic” or unknown molecule. It concerns authorised substances, legally manufactured and distributed, whose use becomes problematic when they enter parallel supply channels or resale networks.

Source

Direction Nationale du Renseignement et des Enquêtes Douanières – DNRED (2025).On la surnomme « la drogue du pauvre » : le trafic de prégabaline en hausse en France. Direction Nationale du Renseignement et des Enquêtes Douanières – DNRED.
Available online:
https://www.linkedin.com/posts/direction-nationale-du-renseignement-et-des-enqu%C3%AAtes-douani%C3%A8res_on-la-surnomme-la-drogue-du-pauvre-l-activity-7430284047429574656-2fZY

Analysis hair proteomic forensic Forenseek

Identifying an individual without DNA: Hair shaft proteomic analysis

News, Scientific progress, ,

When a hair or body hair is recovered without its root from a crime scene, no conventional genetic analysis can be performed. Lacking nuclear DNA, this biological material has long offered only limited evidentiary value and could neither support the formal identification of an individual nor allow comparison with national DNA databases. Since few years, however, a major shift has occurred: hair proteomics, which exploits the proteins of the hair shaft to reveal individualizing markers. Thanks to advances in mass spectrometry, this approach now provides a new pathway for identification, particularly useful in cold cases or in situations where DNA is absent or unusable.

A biological evidence long underused

Hairs recovered from crime scenes are frequently rootless, preventing any STR (Short Tandem Repeat) analysis. Traditional alternatives (morphological examination or mitochondrial DNA analysis), offer only limited discriminating power [1][9]. In many cases, these items were classified as “weak traces,” with insufficient probative value. Yet a hair is biologically rich. It is composed mainly of keratins and other structural proteins that exhibit remarkable stability and resistance to heat, aging, and environmental degradation [1]. This robustness has led several research teams to explore another avenue: instead of seeking nuclear DNA where it is absent or degraded, why not rely directly on proteins, some of which vary between individuals?

Figure 1: Structure of a hair shaft. Source: cosmeticsdesign.com

From DNA to proteomics

This technological shift relies on high-resolution mass spectrometry (HRMS), combined with bioinformatic analysis of protein polymorphisms. Recent work has confirmed that hundreds of proteins can be identified in a single hair shaft. Among them, certain markers, SAPs (Single Amino acid Polymorphisms), directly reflect individual genetic variation [2]. A major study demonstrated that a single individual presents, on average, more than 600 detectable protein groups and more than 160 polymorphic markers, yielding Random Match Probabilities (RMP) on the order of 10⁻¹⁴ [2]. This protein signature therefore offers strong discriminating power, in some cases comparable to the informational value of mitochondrial DNA, while avoiding several well-known limitations of the latter [10].

Technical obstacles related to protein extraction, made difficult by the highly cross-linked structure of keratin, have also been partially overcome. Protocols combining controlled heat and reducing agents now allow more efficient and reproducible extraction [3]. These advances make the approach more mature and more suitable for forensic practice.

Analyse protéomique du cheveu pour une identification forensique. Article Forenseek.
Figure 2: Hair proteomic analysis workflow. Proteins extracted from the hair shaft are fragmented and then analyzed by mass spectrometry to identify individual peptide variations. Source: [2] Parker, G. et al., Deep Coverage Proteome Analysis of Human Hair Shafts, Journal of Proteome Research, 2022.

Concrete opportunities for investigations

Hair-shaft proteomics significantly enhances the usefulness of hair traces in investigations. In cold cases, hairs preserved for decades can now provide individualizing information, even when nuclear DNA was unusable at the time of the original analysis [5]. In extreme contexts (fire scenes, carbonized remains, or highly degraded traces), proteins often persist where DNA has degraded, making them particularly valuable [5][6].

In recent investigations (sexual assaults, abductions, violent incidents, close-contact events), head or body hairs without roots recovered from clothing, vehicles, or victims can now contribute to establishing associations or excluding individuals. Even when it does not yield a formal identification, the protein signature may narrow the suspect pool, confirm or refute an investigative hypothesis, and support evidential assessments presented to judicial authorities [4]. From a legal standpoint, this method must be understood as a probabilistic approach, similar in principle to mitochondrial DNA analysis but based on more stable markers [7]. When integrated carefully, it may become decisive in investigative orientations, the re-examination of older cases, or situations previously left unresolved due to lack of nuclear DNA or usable fingerprints.

Technical limits and challenges

Despite its potential, hair-shaft proteomics remains a technique still in maturation. The first limitation lies in the protocols themselves: protein extraction remains challenging due to the resistant structure of the hair shaft, and full standardization has not yet been achieved [3]. A second challenge is the creation of sufficiently large population databases to compute robust Random Match Probabilities [4]. Inter-laboratory validation, essential before any use in judicial contexts, requires testing on hairs from individuals of different populations, ages, environments, and storage conditions [4][6].

Legal integration also presents challenges. Judges and attorneys will need clear explanations of this emerging probabilistic evidence. Classical admissibility requirements (reliability, reproducibility, methodological transparency, statistical robustness), apply fully [7]. To date, no international standard formally regulates the procedure, although preliminary work is underway [8].

Towards standardization and operational integration?

The outlook for the coming years is particularly promising. Several centres, notably Murdoch University and ChemCentre near Perth, Australia, are working on protocol standardization and the development of diverse reference databases [5][6]. Advances in mass spectrometry and bioinformatic tools now make possible a partial automation of analyses and more seamless integration into routine forensic laboratory workflows. For investigators, police officers, magistrates and forensic experts, this evolution requires adapting collection and preservation practices. From now on, any rootless hair should be systematically collected and retained. Even very small or very old samples may contain an exploitable protein signature. This shift in perspective could transform the re-evaluation of cold cases, fire-scene examinations, and the most complex investigations.

Conclusion

Hair-shaft proteomics represents one of the most promising advances of the coming years in forensic identification. By restoring value to traces long considered underexploited, it offers a reliable and robust alternative when DNA is absent, degraded or otherwise unusable. Although judicial integration still requires validation, standardization and appropriate communication, early results clearly indicate that this approach could play a decisive role in complex investigations, degraded scenes and unresolved cases.

References :

[1] Adav, S.S., Human Hair Proteomics: An Overview, Science & Justice, 2021.
[2] Parker, G. et al., Deep Coverage Proteome Analysis of Human Hair Shafts, Journal of Proteome Research, 2022.
[3] Liu, Y. et al., Individual-specific proteomic markers from protein amino acid polymorphisms, Proteome Science, 2024.
[4] Smith, R.N. et al., Forensic Proteomics: Potential and Challenges, Proteomics, 2023.
[5] Murdoch University – Western Australia, Hair Protein Identification Project (2024–2025).
[6] ChemCentre (Western Australia Government), World-first Forensic Proteomics Research Program, 2024.
[7] Henry, R. & Stoyan, N., The Admissibility of Proteomic Evidence in Court, SSRN, 2020.
[8] ISO / ASTM – Guidelines on Forensic Biology & Novel Analytical Methods, 2022–2024.
[9] Anslinger, K., Hair Evidence in Forensic Science, Wiley, 2019.
[10] Budowle, B., Mitochondrial DNA in Forensic Identification, Elsevier, 2018.

Towards a revolution in post-mortem forensic imaging

Forensic medecine, News, ,

How can an internal lesion go unnoticed during autopsy yet may have potentially caused death? In forensic medicine, understanding internal trauma is essential to reconstructing the sequence of a violent event. Among such injuries, those involving the vertebral artery present a major challenge. Subtle and often concealed by bone structures, they frequently escape traditional examination methods. A recent technological breakthrough in forensic imaging offers a promising approach: combining fluoroscopy and micro-computed tomography (micro-CT) to analyze post-mortem vascular injuries with unprecedented precision.

Key artery, difficult access

The vertebral artery supplies vital regions of the nervous system, including the brainstem, cerebellum, and posterior areas of the brain. Even a minor injury can trigger a stroke, a rapid neurological collapse, or sudden death. Its anatomical pathway, deeply embedded within the cervical spine, makes it particularly difficult to explore. In a forensic context, a lesion affecting this artery represents a critical clue when analyzing a penetrating neck wound, often revealing a potentially lethal intent.

Forensic imaging to observe real-time blood flow

The vertebral artery supplies vital regions of the nervous system, including the brainstem, cerebellum, and posterior areas of the brain. Even a minor injury can trigger a stroke, a rapid neurological collapse, or sudden death. Its anatomical pathway, deeply embedded within the cervical spine, makes it particularly difficult to explore. In a forensic context, a lesion affecting this artery represents a critical clue when analyzing a penetrating neck wound, often revealing a potentially lethal intent.

Micro-CT: diving into the heart of the lesion

To overcome this limitation, researchers have turned to micro-computed tomography (micro-CT), a very high-resolution imaging technique. The sample is rotated during the acquisition of thousands of radiographic images, which are then reconstructed into a digital 3D model. This process reveals otherwise invisible details such as arterial wall tears, thrombi, dissections, or partial ruptures. These reconstructions allow for virtual dissections from multiple angles without altering the body, ensuring a high level of reproducibility, an invaluable feature in forensic investigations.

A standardized method serving both justice and medicine

The protocol developed by Secco and colleagues relies on ex situ imaging, meaning that the examination is performed on an artery extracted from the body. This approach overcomes several obstacles, such as advanced decomposition, previous surgery, complex trauma, or movement artifacts. With the injection of a contrast agent, the vascular network becomes clearly visualized, allowing for precise and stable documentation. These high-quality images serve as robust evidence admissible in court and represent a valuable resource for medical teams involved in planning neurosurgical or trauma-related procedures.

An educational and scientific tool

Beyond their diagnostic value, 3D reconstructions and fluoroscopic videos serve as outstanding educational tools. They allow for a strikingly realistic visualization of injury mechanisms and a deeper understanding of the biomechanics of penetrating trauma. This refined comprehension of the forces at play helps not only researchers characterize vascular lesions, but also engineers design more effective protective equipment and forensic experts accurately reconstruct the circumstances surrounding a violent act.

Towards a new standard in forensic medicine

Born from close collaboration between radiologists, pathologists, engineers, and chemists, this imaging protocol represents a major step forward in forensic practice. The growing accessibility of micro-CT equipment suggests its forthcoming integration into routine autopsies. With the continuous improvement of imaging technologies in terms of resolution, speed, and multi-contrast capacity, the prospect of non-invasive post-mortem vascular examinations is becoming increasingly realistic. In the long term, this method could be extended to other arterial regions (carotid, subclavian, intracranial), thereby deepening our overall understanding of vascular trauma.

Conclusion

At the crossroads of technology and forensic science, this approach combines precision, rigor, and innovation. By providing a three-dimensional and reproducible reading of internal injuries, it transforms the way stab wounds involving the vertebral artery are analyzed. This is a major advancement, serving both judicial truth and scientific knowledge, and it paves the way for a new generation of autopsies that are finer, more reliable, and better documented.

References  :

Bioengineer.org. (2024). Detecting Vertebral Artery Stab Wounds with Imaging. Read here.

Secco, L., Franchetti, G., Viel, G. et al. Ex-situ identification of vertebral artery injuries from stab wounds through contrast-enhanced fluoroscopy and micro-CT. Int J Legal Med (2025). Read here.

Medscape. (2024). Vertebral Artery Anatomy. Read here.

Post-traumatic symptoms in individuals who were victims of childhood sexual abuse

Articles, Justice, News

The clinical and judicial assessment of children who are victims of sexual abuse requires an in-depth understanding of child development and of the manifestations of post-traumatic symptoms that are typical of childhood and adolescence. Recognizing the specific symptom patterns in children makes it possible to distinguish traumatic manifestations from normal developmental variations, within an approach that must necessarily respect the child’s world.

Respecting and building upon the child’s world

Working with children involves using mediating tools that correspond to their developmental world, employing language and tone appropriate to their age, and exploring their personal interests. Beyond the therapeutic alliance that this fosters, a child’s interests also serve as indicators of their developmental level, environment, and daily organization. These are valuable cues for forensic evaluation.

For instance, consider an 8-year-old child in second grade who, when simply asked about his favorite activities, mentions playing a Paddington game on a tablet. When gently questioned about the tablet and the game, through prompts such as “What do you like about this game?” or “Can you tell me more about this tablet?”, the child explains that the tablet belongs to his father, that he does not have one of his own, and that he is allowed to play on it on Wednesdays and weekends for 30 minutes in the family living room. He says he likes the little bear for his adventures, and is then asked to describe one of his favorite moments.

Respecting the child’s world means striving to avoid the risk of retraumatization during the forensic examination.

The child’s responses allow the evaluator to assess several aspects: an interest and activity consistent with their developmental age, a family framework appropriate for their age regarding screen use, and the child’s ability to construct a narrative (use of pronouns and tenses, spatial and chronological structuring, distinction between imagination and reality, etc.). The interpretation will naturally differ if the child plays a game such as Call of Duty, a war-themed game, rated 16+ or 18+ depending on the version, if the 8-year-old has a screen in their bedroom, or if the subject is instead a 15-year-old adolescent.

Finally, and in my view, most importantly, respecting the child’s world means striving to prevent the risk of retraumatization during the forensic examination. Creating an environment that signals to children they are welcome is essential: children’s books in the waiting area, toys, comfortable seating, and the freedom to move around. Advising caregivers to bring a comfort object or soft toy (doudou) is also important. Returning to the question of post-traumatic symptomatology in children, this issue takes on a particular resonance in light of recent cases such as that of Joël Le Scouarnec, in which 299 identified victims exhibited significant post-traumatic symptoms despite an apparent absence of conscious memories of the assaults committed under anesthesia.

The theoretical framework of sexual psychotrauma

The psyche refers to the entirety of conscious and unconscious mental phenomena: cognitive processes (thought, memory, perception), affective processes (emotions, feelings), psychological defense mechanisms, fantasy and imaginative activity, and personality structures. A traumatic event represents a violent intrusion into the psyche, exceeding the mental apparatus’s capacity for processing and integration what is referred to as traumatic breach (effraction traumatique).

A child who has been sexually abused often remains in denial for a long time

Traumatic breach in a child who has been sexually assaulted presents particular characteristics. Louis Crocq (1999) defines psychotrauma as “a phenomenon involving a breach of the psyche and the overwhelming of its defenses by violent stimuli linked to the occurrence of an event that is aggressive or threatening to the life or integrity (physical or psychological) of an individual who is exposed to it as a victim, witness, or actor.” In cases of sexual assault, this breach takes on a dimension that is beyond the child’s psychological comprehension. As Tardy (2015) points out, “A child who has been abused often remains in denial for a long time, a defense mechanism aimed at avoiding the realization that the adults supposed to protect them were, in fact, the aggressors, which would be too distressing to acknowledge.”

The repetition syndrome, as described by Crocq (2004), is defined as “a set of clinical manifestations through which the traumatized patient involuntarily and repeatedly relives their traumatic experience with great intensity.” Thus, in children and adolescents, as in adults, numerous symptoms related to repetition or avoidance of repetition can be observed.

Age-specific symptoms: a developmental approach

Traumatic manifestations in younger children:

They are characterized by poorly integrated intrusive recollections, consisting mainly of intense sensations and emotions, as described by Eth and Pynoos (1985) and by Pynoos, Steinberg et al. (1995). Beyond ordinary childhood play, specific play behaviors linked to the traumatic event may emerge. These post-traumatic play patterns represent a major clinical indicator. Fletcher (1996) describes them as “repetitive, involving a central element connected, or sometimes not connected, to the event, less elaborate and imaginative than typical play, generally emotionally charged (anxiety), rigid, and joyless.” Such play loses its normal creative and exploratory function, becoming compulsive and stereotyped.

Neurovegetative hyperarousal and avoidance are common post-traumatic symptoms. In children, they manifest as anxious hypervigilance, exaggerated startle responses, and sleep disturbances with frequent awakenings. Avoidance may take the form of social withdrawal, emotional numbing, and developmental regression affecting toilet training, sleep, or the reemergence of early childhood fears. In his longitudinal study of 166 sexually abused children, Putnam (2003) found that 40% developed hyperactivity symptoms within six months following disclosure, compared to 8% in the general population. The author interprets this hyperactivity as an adaptive flight response to intrusive post-traumatic stimuli.

Some children develop overly smooth, inconspicuous behaviors that draw no attention at all.

Post-traumatic manifestations in children often display little-known specificities that make their identification particularly complex. Unlike adults, children frequently present with nonspecific symptoms according to developmental research, especially younger children (under six years old).

From the earliest age, disturbances in body awareness and bodily experience constitute a key clinical marker: restriction in clothing choices or adoption of sexualized clothing, extreme washing behaviors, difficulties with nudity, poor bodily investment, a devalued image of their body or of certain body parts, disturbances in tactile relationships, and avoidance of affectionate gestures. These bodily manifestations often go unrecognized because they may appear trivial or be attributed to other causes. In contrast to the agitation sometimes observed, some children develop overly smooth, inconspicuous behaviors that draw no attention at all. This inhibited presentation, characterized by excessive compliance and extreme conformity, paradoxically constitutes a warning sign. Research emphasizes the importance of “keeping in mind that some of these behaviors are common in this age group. Thus, symptoms of neurovegetative hyperarousal are expressed more as an intensification of behaviors already present in the child, sometimes difficult for significant others to notice” (Eth & Pynoos, 1985; Pappagallo, Silva & Rojas, 2004).

Older children (6 to 12 years old):

In addition to the previously described symptoms, children in this age group may present somatic complaints (headaches, abdominal pain, etc.) which, due to their nonspecific nature, are not always associated with sexual trauma. Nevertheless, these somatic manifestations are important clinical indicators within a comprehensive assessment.

In school-aged children, intrusive memories become more structured but may include protective cognitive distortions that minimize the severity of the event. Post-traumatic play also evolves: it becomes “more elaborate and sophisticated, involving transformation of certain aspects of the event, the introduction of symbolic dangers (monsters), and the inclusion of other people (peers)” (Fletcher, 1996). These transformations reflect an attempt at more mature psychological processing. School functioning often becomes significantly affected, with attention difficulties, declining academic performance, anxiety-related school refusal, as well as diminished self-esteem and reduced trust in caregivers. Frequent somatic symptoms may also lead to school absenteeism.

Adolescence :

Drawings and post-traumatic play become rare, replaced by other modes of expressing distress. Manifestations resemble those observed in adults (Yule, 2001; Rojas & Lee, 2004), with recurrent memories, flashbacks, and pronounced emotional numbing, that is, a marked reduction in the intensity and range of emotional expression. Emotional numbing manifests through diminished or fixed facial expressions, a monotone voice, dull or inexpressive eyes, inappropriate or absent emotional responses, and a reduced capacity to feel joy, sadness, or anger. It may lead to difficulties forming emotional bonds, impoverished interpersonal relationships, and an impression of “coldness” perceived by others. Addictive behaviors may emerge, involving either substances (alcohol, drugs, toxic products) or activities (video games, pornography, sexual behaviors, gambling), along with risk-taking behaviors (speeding, dangerous stunts, delinquent acts).

The assessment must distinguish between normal sexual exploration and pathological manifestations.

Specific symptoms of sexual trauma

Disturbances in body awareness and bodily experience are characteristic and represent a specific marker of physical and sexual trauma. Overall, the sexualization of language and behaviors is a strong indicator, particularly when the change appears suddenly.

Problematic Sexual Behaviors (PSB) represent a specific manifestation that is especially important to identify. According to the ATSA (Association for the Treatment of Sexual Abusers), PSB are defined as “sexual behaviors displayed by a child that are considered inappropriate for their age or level of development” and that may be “harmful to the child themselves or to other children involved.”

PSB are defined in children up to age 12, and their assessment requires a solid understanding of child and adolescent sexual development, as well as the use of age-appropriate language. This definition follows a developmental approach in which assessment must distinguish normal sexual exploration from pathological manifestations. According to Chaffin et al. (2006), sexual behaviors are considered problematic when they meet one or more of the following six criteria: they occur with “high frequency or intensity,” “interfere with the child’s social or cognitive development,” “involve force, coercion, or intimidation,” are “associated with physical injury or emotional distress,” “occur between children of different developmental stages,” and “persist despite adult intervention.” PSB may include sexual touching of other children, excessive masturbation, sexual knowledge that is inappropriate for the child’s developmental stage, or hypersexualized behaviors.

Symptoms in adulthood:

Longitudinal studies demonstrate the persistence of symptoms into adulthood. A British study of 2,232 18-year-old participants revealed an increased risk of psychiatric disorders: 29.2% presented with major depression, 22.9% with conduct disorders, 15.9% with alcohol dependence, 8.3% with self-harming behaviors, and 6.6% with suicide attempts.

The impact on intimate and marital life is particularly well documented. According to Gérard (2014), nearly 60% of adults who were sexually abused in childhood experience relationship isolation, and 20% have never been able to form a long-term partnership. Relational difficulties are characterized by a paradoxical oscillation between excessive mistrust and dependence, polymorphic sexual disturbances (“hypersexuality or lack of libido, absence of pleasure, pain, risky sexual behaviors”), and the search for a “repairing” partner that often leads to intense frustration. Among women, specific menstrual disturbances are frequently reported from puberty onward: irregularities, pain, amenorrhea, and feelings of disgust.

In forensic evaluations of adults who were sexually abused as children, many of the same symptoms observed in childhood may reappear: persistent masturbatory behaviors originating around the time of the abuse or its disclosure, avoidant somatizations, and attention difficulties. Collecting these clinical indicators can help establish coherence with the events described in the context of psychological expertise. Moreover, for the victim, such analysis can provide meaning to behaviors that were previously misunderstood or socially disapproved of.

It is not necessary to remember in order to suffer from post-traumatic symptoms

The Scouarnec case: symptoms without memory

The Scouarnec case illustrates perfectly the issue of post-traumatic symptoms in the absence of conscious memory. The 299 identified victims, mostly minors who were assaulted under anesthesia, exhibited symptomatic manifestations even before the facts were revealed by investigators. Amélie Lévêque testified: “I actually had so many aftereffects from that operation that were there, but no one could explain them.” These sequelae included medical phobias, eating disorders, and “the diffuse feeling that something abnormal had happened.” Expert witnesses at the trial confirmed that “it is not necessary to remember in order to suffer from post-traumatic symptoms.

Jean-Marc Ben Kemoun, child psychiatrist and forensic doctor, explains this phenomenon as the “memory of the body”: “The body speaks, and the less we are consciously aware of a painful or stressful event, the stronger its impact on the body.” Even in an altered state of consciousness, the traumatic impact persists, generating long-lasting symptoms in the absence of explicit memory.

Clinical implications and perspectives

This clinical reality underscores the importance of a multidimensional assessment that respects developmental particularities. Forensic evaluation must include the observation of play and interests according to age, assessment of social and academic adjustment, and evaluation of the individual’s ability to project themselves positively into the future. The Scouarnec case demonstrates that the absence of conscious memories in no way excludes the existence of trauma and its lasting consequences. This understanding is essential for a symptom-based clinical assessment, particularly in young children or in individuals who experienced sexual trauma before the age of six.

Bibliographie :

Crocq, L. (2004). Traumatismes psychiques : Prise en charge psychologique des victimes. Paris : Masson.

Tardy, M.-N. (2015). Chapitre 8. Vécu de l’enfant abusé sexuellement. Dans M.-N. Tardy (dir.), La maltraitance envers les enfants. Les protéger des méchants (pp. 123-150). Paris : Odile Jacob.

Drell, M. J., Siegel, C. H., Gaensbauer, T. J. (1993). Post-traumatic stress disorder. Dans C. H. Zeanah (dir.), Handbook of infant mental health (pp. 291-304). New York : Guilford Press.

Fletcher, K. E. (1996). Childhood posttraumatic stress disorder. Dans E. J. Mash & R. A. Barkley (dir.), Child psychopathology (pp. 242-276). New York : Guilford Press.

Frank W. Putnam, Ten-Year Research Update Review: Child Sexual Abuse, Journal of the American Academy of Child & Adolescent Psychiatry, Volume 42, Issue 3, 2003, Pages 269-278,

Pynoos, R. S., Steinberg, A. M., Wraith, R. (1995). A developmental model of childhood traumatic stress. Dans D. Cicchetti & D. J. Cohen (dir.), Developmental psychopathology (Vol. 2, pp. 72-95). New York : Wiley.

Scheeringa, M. S., Zeanah, C. H. (2003). Symptom expression and trauma variables in children under 48 months of age. Infant Mental Health Journal, 24(2), 95-105.

Yule, W. (2001). Post-traumatic stress disorder in the general population and in children. Journal of Clinical Psychiatry, 62(17), 23-28.

Gérard, C. (2014). Conséquences d’un abus sexuel vécu dans l’enfance sur la vie conjugale des victimes à l’âge adulte. Carnet de notes sur les maltraitances infantiles, 3, 42-48. DOI : 10.3917/cnmi.132.0042

Chaffin, M., Letourneau, E., Silovsky, J. F. (2002). Adults, adolescents, and children who sexually abuse children: A developmental perspective. Dans J. E. B. Myers, L. Berliner, J. Briere, C. T. Hendrix, C. Jenny, & T. A. Reid (dir.), The APEAC handbook on child maltreatment (2e éd., pp. 205-232). Thousand Oaks, CA : Sage.

Chaffin, M., Berliner, L., Block, R., Johnson, T. C., Friedrich, W. N., Louis, D. G., … & Silovsky, J. F. (2006). Report of the ATSA task force on children with sexual behavior problems. Child Maltreatment, 11(2), 199-218.

Gury, M.-A. (2021). Pratique de l’expertise psychologique avec des enfants dans le cadre judiciaire pénal. Psychologues et Psychologies, 273, 24-26.

France Info (6 mars 2025). Procès de Joël Le Scouarnec : une affaire “entrée par effraction” dans la vie de nombreuses victimes, sans souvenirs d’actes subis sous anesthésie.

France 3 Bretagne (14 avril 2025). Procès le Scouarnec : “même sans souvenirs, on peut souffrir de troubles post-traumatiques”. consultable ici.

Pôle fédératif de recherche et de formation en santé publique Bourgogne Franche-Comté (2025). Aide au diagnostic et au repérage ajusté du comportement sexuel problématique chez l’enfant. Projet de recherche AIDAO-CSP.

Reconstruction of torn documents

News,

When a document has been torn or shredded, the investigator is faced with a puzzle that has lost its box, its reference image, and sometimes even a portion of its pieces. Yet, the information contained within those fragments can alter the course of a case: a single figure in a contract, a name in a table, or a handwritten note in the margin. The question is therefore not merely “can it be reconstructed?”, but rather “can it be done reliably, traceably, and fast enough to be of use to the investigation?”

Why reconstruction is challenging

In forensic practice, fragments are rarely clean or uniform. They vary in shape, size, paper texture, ink density, and orientation. When several documents have been destroyed together, the fragments intermingle and create visual ambiguities: two edges may appear to fit when they do not, two different fonts may look similar, and uniform areas, blank backgrounds or low-detail photographs, provide almost no clues. So-called edge-matching approaches, which seek continuities along borders and patterns, work fairly well for small sets. But as the number of fragments grows, the number of possible combinations increases exponentially, and these methods struggle to discriminate between competing hypotheses.

The idea: harnessing randomness to explore better

Stochastic optimization offers an alternative way to approach the problem. Rather than attempting to reach the perfect configuration immediately, the algorithm generates plausible assemblies, evaluates them, and occasionally accepts “imperfect” choices in order to continue exploring the solution space. This probabilistic strategy continuously alternates between two complementary phases: exploration, which searches new pathways to avoid dead ends, and exploitation, which consolidates promising insights already discovered. In practice, each proposed assembly is assigned a score based on visual continuity (alignment of letters, extension of strokes, texture and color matching). If coherence improves, the hypothesis is adopted; if it deteriorates, it may still be tolerated for a while to test whether it leads to a better configuration later on. This flexible logic distinguishes the method from more rigid approaches such as simulated annealing or certain genetic algorithms. It adapts better to the real variability of documents and fragment mixtures, and it leaves room for light operator interaction when needed.

What the experiments show

The authors report large-scale tests conducted on more than a thousand heterogeneous torn documents (office printouts, handwritten pages, images, and mixed-content sheets). The results converge toward an observation intuitive to any expert: the richer a document is in content (dense text, grids, or patterns), the faster and more accurate the reconstruction process becomes. Conversely, uniform areas require more iterations because they provide few visual anchor points. In the most challenging cases, occasional operator input, such as confirming a match or indicating the probable orientation of a fragment, is sufficient to guide the algorithm without compromising overall reproducibility.

Validation through a benchmark challenge

To evaluate the method under conditions close to real-world scenarios, the researchers tested it on fragment datasets inspired by the DARPA Shredder Challenge, a well-known benchmark in which participants attempt to reconstruct documents shredded into very narrow strips or confetti-like pieces. The method successfully reconstructed coherent and readable pages where other techniques either failed or stalled. This is more than an academic result: it demonstrates that the algorithm performs robustly when faced with investigative constraints, including numerous, intermingled, and occasionally damaged fragments resulting from handling or scanning.

Relevance to forensic practice

Beyond raw performance, the value of such a method lies in its integration into a demonstrable forensic workflow. The initial reconstruction phase, typically the most time-consuming, can be largely automated, freeing analysts to focus on content examination. More importantly, the approach lends itself to precise traceability: a log of tested hypotheses, retained parameters, acceptance thresholds, and intermediate captures. These records help document the chain of custody, justify technical choices before a magistrate, and, when necessary, reproduce the procedure in full transparency.

In laboratory settings, integration is facilitated by adopting rigorous acquisition practices such as high-resolution scanning, neutral backgrounds, color calibration, and systematic archiving of source files. A preliminary physical sorting of fragments, by paper weight, hue, or the presence of images, also enhances robustness by reducing ambiguities at the input stage.

Limitations and avenues for improvement

As with any optimization method, performance depends heavily on proper parameter tuning. Thresholds that are too strict will hinder exploration, while overly permissive criteria make it erratic. Highly mixed batches, comprising visually similar documents with identical layouts or fonts, remain difficult and may require occasional human intervention to prevent mismatches. Micro-fragments produced by high-grade shredders represent another major challenge: the smaller the visible surface, the fewer cues the algorithm can exploit. Future progress is expected in improving robustness against scanning artifacts, automating pre-sorting steps, and, more broadly, establishing standardized performance metrics (such as edge-matching accuracy, page completeness, and computation time) to facilitate fair comparison between methods.

Conclusion

Reconstructing torn documents is no longer solely a matter of expert patience and intuition. Stochastic optimization provides an exploration engine capable of handling large volumes, managing uncertainty, and producing usable assemblies. By combining automation, traceability, and expert supervision when needed, this approach transforms an “impossible puzzle” into a systematic procedure, serving the purposes of material evidence, intelligence gathering, and the preservation of damaged archives.

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