Each year, the forensic units of the National Police and the National Gendarmerie detect and recover several hundred thousand fingerprint, palm-print and even footprint impressions on a wide range of surfaces, linked to hundreds of thousands of delictual or criminal offences (burglaries, vehicle thefts, drug trafficking, armed robberies, rapes, homicides, terrorist attacks, etc.).
– text translation in order of appearance: Friction ridge impressions Crime scene – do not cross Ridge ending, lake, short ridge / fragment ; suitable print First responder, victim, witness, janitor, relative of the victim ; suspect No match Loading 6,5 millions (in 2021) ; Automated Fingerprint Database (FAED) (french equivalent of AFIS) data transfer into the database ; retention period 15 to 25 years ; fingerprint hit —
Since the Francisca Rojas case in Argentina in 1892 (1) and the identification of Henri-Léon Scheffer in France in 1902 by Alphonse Bertillon (2), this form of physical evidence has made it possible to identify offenders through the latent prints they leave behind at crime scenes.
International practice in fingerprint identification is not standardized. In France, in order to link a latent print recovered from a crime scene to a friction ridge impression taken from a suspect, forensic experts rely on two approaches:
• The 12-point numerical standard
• The probabilistic or holistic approach
For nearly a century, the binary view of fingerprint identification based on the “12-point standard” has gradually given way to a continuum of possible conclusions. Depending not only on the number but also on the quality of the minutiae present in the questioned print, experts use a numerical and verbal scale of comparative assessment that may point more or less strongly toward identification or exclusion.
At present, this probabilistic approach is applied only in complex fingerprint examinations. The 12-point numerical standard continues to be used routinely in France—see our video on the recovery and comparison of friction ridge impressions.
Amendment to Article 55-1 of the French Code of Criminal Procedure
In the course of a flagrante delicto investigation, Article 55-1 of the French Code of Criminal Procedure expressly provides that, during the judicial inquiry, samples may be taken from any person concerned by the procedure. Such samples may prove necessary to carry out technical and scientific examinations for comparison with traces and evidence collected as part of the investigation. Under what conditions may these samples be taken?
What does Article 55-1 of the CCP provide?
The judicial police officer may, personally or under his or her supervision, collect external samples from any person likely to provide information on the facts in question, or from any person against whom there are one or more plausible reasons to suspect that they have committed or attempted to commit the offence. These samples are necessary to carry out technical and scientific examinations for comparison with traces and evidence collected for the purposes of the investigation.
The officer also carries out, or has carried out under his or her supervision, the collection of identifying information, in particular the taking of fingerprints, palm prints or photographs necessary for the feeding and consultation of police databases, in accordance with the rules applicable to each of these files.
Refusal by a person against whom there are one or more plausible reasons to suspect that they have committed or attempted to commit an offence to submit to the sampling operations mentioned in the first and second paragraphs, as ordered by the judicial police officer, is punishable by one year of imprisonment and a €15,000 fine.
In decision no. 2003-467 DC, the Constitutional Council held, with respect to Article 30 of the Law of 18 March 2003 on Internal Security, ‘that the expression “external sampling” refers to a sampling procedure that does not involve any internal bodily intervention; that it therefore entails no painful, intrusive or degrading methods affecting the dignity of the persons concerned; that, accordingly, the claim alleging a violation of the inviolability of the human body is unfounded; that external sampling does not, moreover, adversely affect the individual liberty of the person concerned’ (para. 55).
Fingerprinting under coercion:
Article 30 of Law no. 2022-52 of 24 January 2022 on Criminal Liability and Internal Security supplements Article 55-1 of the French Code of Criminal Procedure with the following paragraph:
« Without prejudice to the application of the third paragraph, where the taking of fingerprints, palm prints or a photograph is the sole means of identifying a person interviewed under Articles 61-1 or 62-2 for a felony or a misdemeanour punishable by at least three years’ imprisonment, and who refuses to provide proof of identity or supplies manifestly false identity information, this operation may be carried out without that person’s consent, with written authorisation from the public prosecutor, upon a reasoned request by the judicial police officer. The judicial police officer, or under his or her supervision a police officer, shall resort to coercion only to the extent strictly necessary and in a proportionate manner, taking into account, where appropriate, the vulnerability of the person. A report shall be drawn up of this operation, stating the reasons why it constituted the sole means of identifying the person, as well as the date and time when it was carried out. The report shall be transmitted to the public prosecutor, with a copy provided to the person concerned. »
Finally, a French website that aims to promote not only the reliability of results through the acceptance of questioning the knowledge and truths proclaimed by “experts” (which aligns rather well with our distinctly French critical mindset), but also the emergence of a new discipline: “forensic” science, which deals with inferences drawn from the study of effects in order to approach their underlying causes. On this site, we will therefore not be subjected to dogmas, technological quarrels, or axioms, but rather be encouraged to awaken a “forensic” way of thinking that is open to society, to critique, and firmly modern and universal in its technical application.
To assist the reader of this site, it is essential to define the terminology employed by the “experts” working towards the pursuit of truth in criminal trials within the judicial system. Just as law, the Navy, or medicine have their own specialized vocabulary, so too do the sciences, and the use and precision of this vocabulary are necessary to understand their results or demonstrations. The absence of bias in the reporting of findings and the linguistic clarity of conclusions largely contribute to the acceptance of judicial decisions or of the “right to punish” that is vested in Justice in our societies.
It is therefore indispensable to distinguish “criminology,” which concerns itself with the social phenomenon of crime, from “criminalistics,” which is the use of scientific methods, belonging to the exact sciences, to study or evaluate traces found at crime scenes. The Code of Criminal Procedure, in its Article D.7, refers to “technical and scientific police operations,” in order not to differentiate between the detection, collection, preservation, or exploitation of traces. These specialties will not be addressed directly in this article. Instead, we will consider the field of “forensic sciences,” representing the practical application of all the “exact” sciences to the pursuit of truth in criminal trials, sciences whose role is to shed light for the judge in the decision-making process. To illustrate this point, I would say that if the position of celestial bodies were relevant to solving a crime, forensic sciences would include astrophysics, but not astrology.
Naturally, this leads us to the emergence of “Forensic” science in the singular, to demonstrate that, as a result of numerous theoretical contributions regarding the study of effects to determine causes, the reasoning and techniques employed in approaching the crime scene have now given rise to a distinct science in its own right: “forensic,” a discipline open to history, economics, and innovation, but also to evolution and intrinsic critique, no longer limited to the mere application of another science (physics, chemistry, genetics, etc.) to the judicial domain of trace evidence examination. As with other sciences, peer-reviewed journals dedicated specifically to forensic science have thus emerged.
Forensic Science Institute of the French Gendarmerie – IRCGN
From the moment justice sought to uncover the truth through demonstration rather than relying on divine judgment (ordeals), it turned to knowledgeable individuals in relevant fields for guidance. Within the inquisitorial system, as early as the fifteenth century, midwives, surgeons, and physicians were called upon by the courts to determine the nature of a crime, cases of infanticide, to examine a body in order to establish the time of death, the type of injuries, their lethality, or to identify the weapon used. Thus, given the diversity of crimes, all trades quickly became “required,” such as notaries for forged documents, goldsmiths for counterfeit jewelry, or carpenters for break-ins, until the development of specialized sciences in the late nineteenth century brought increasingly advanced expertise—chemistry, toxicology, physics, and even mathematics, as exemplified during the Dreyfus trial. Today, experts organized into professional associations assist magistrates in nearly every country in the world.
The more justice seeks precision in its decision-making, the more it turns to experts to shed light on its judgments and establish the moral or material causality of offenses. France occupies a special place within the global forensic community, due to the theorization, in the early twentieth century, by Dr. Edmond LOCARD[1], of this specific approach to the crime scene, through the formulation of a fundamental principle: “every contact leaves a trace. It is impossible for a criminal to act, especially considering the intensity of a crime, without leaving numerous marks of his presence. Sometimes the offender leaves behind traces of his activity at the scene, while at other times, through a reverse action, he carries away on his body or clothing indications of his presence or his actions.” This clear statement underlines the necessity of trace evidence detection by investigators at crime scenes in order to substantiate the offense and identify its perpetrator.
A second principle essential to forensic sciences was articulated by Paul Leland KIRK (1902–1970): “Every object in our universe is unique. Two objects of common origin can be compared, and individualization can be established if the objects possess sufficient quality to permit the observation of their individuality.”
When these two fundamental principles are combined, one arrives at the scientific demonstration of the individualization of traces and, potentially, of the offender or the location from the traces recovered at a crime scene. Forensic experts constantly strive to identify such individualizing traces, which today are best exemplified by the detection of biological traces left by a perpetrator at a crime scene, enabling the identification of their unique source.
It can thus be concluded that criminalistics seeks to detect and analyze traces and evidence recovered from crime scenes on the basis that the study of effects allows one to infer causes, by applying the first principle—that every contact leaves a trace—and the second—that every trace is individualizing—together with the fact that no two random phenomena ever leave exactly the same traces. Nevertheless, this requires particular caution on the part of those tasked with interpreting results, since the traces discovered by investigators—and those specifically sought[2]—do not reflect all the traces actually present, nor therefore all the effects corresponding to all possible causes.
Signal, Image, and Speech Department (SIP) – Credits: Forenseek
The holistic approach to trace analysis drives innovation, leading industry to continually develop techniques for improved detection (such as the crimescope[3] in the 1980s), better collection of highly informative evidence like genetic traces (swabs in the 2000s), the recovery of invisible digital evidence (radio wave sensors/IoT devices in the 2010s), and, more recently, the development of odor sensors capable of detecting olfactory signatures[4] potentially left behind by an offender wearing a mask and gloves. All these new capabilities are now available to forensic police units worldwide. Forensic science laboratories, meanwhile, employ analytical equipment that is increasingly sensitive, specific, and rapid—producing results that are ever more complex to interpret, and requiring the expertise of highly skilled professionals.
When all the data obtained from the exploitation of these different types of evidence are combined, it becomes indispensable to rely on artificial intelligence tools or data-mining methods, which are now prerequisites for understanding, contextualizing, and exploiting the full range of information derived from a criminal case. Whereas in the 1980s a typical case file comprised around 1,000 pages (readable by a single person), today the investigation involves the processing of gigabytes of data in the form of texts, images, recordings, connection logs, audio files, and a wide variety of highly specialized analytical results. Furthermore, each item of evidence carries a specific weight in the demonstration (Bayesian interpretation), which may vary depending on the context of its discovery. For instance, a DNA trace recovered from a cigarette butt (which could have been transported) does not carry the same probative value as the same DNA trace found on a knife embedded in a victim’s back. In forensic science, this relative probative value is formalized using Bayes’ theorem, which allows the probability of one event to be determined from another event that has occurred, provided the two events are interdependent. Here again we find the pursuit of inference through the study of effects to understand their causes.
Only the use of tools capable of automatically creating relational links within a case file, of computing Bayesian networks to assess the weight of each piece of evidence, of annotators able to contextualize words within sentences or detect temporal or geographical inconsistencies between statements, or of systems able to retrieve a specific image from video recordings, will make it possible to fully comprehend the case, to reconstruct events—in short, to “judge.” The development of tools with fully controlled algorithms, free of the cognitive biases of their designers, is currently under evaluation in forensic science laboratories.
Department of Anthropology and Hemato-Morphology (ANH) – Credits: Forenseek
The capture of all traces present, in every form that technology allows, and their placement within a digital space reconstructing the crime scene, already provides us today with a tool enabling the visualization of such scenes (the digital twin). Yet, far beyond a simple animated reconstruction in augmented reality, the advent of the “metaverse,” integrating all the previously described digital tools, heralds a paradigm shift. A « metaverse » capable of reproducing natural laws (all physical phenomena of the real universe)—the trajectory of a projectile, the fall of a body, the explosion of a bomb and the projection of fragments, even the reconstruction of blood spatter—will enable us to replay scenarios, generate hypotheses, and test them in a theoretical effect/cause feedback loop that can propose alternative sequences of events, redirect the search toward specific traces, or reveal inconsistencies in the discovery of certain evidence. The integration of probabilistic laws into these metaverses will provide investigators and magistrates with a scoring system ranking one hypothesis as more probable than another in light of the traces recovered. The ability to process enormous quantities of data, combined with artificial intelligence algorithms capable of proposing and replaying hypotheses and scenarios, simulating them, and then analyzing their effects to compare and progressively (mathematically) align them with traces found at the crime scene, represents the ultimate step in understanding an event. This should allow the magistrate to come as close as possible to the reality of what occurred.Forensic science, which seeks to reconstruct the past from thousands of data points gathered in the present, opens a field of critical analysis that helps to nourish and shape the overall thinking of our society. Market economies, urbanization, environmental issues, and pandemics raise the same questions of why a situation arises, in order to better adapt to it. Forensic science, in its pursuit of judicial truth in criminal trials, has developed theoretical foundations and tools to address this why and propose a how, thanks to the instruments designed by investigators and forensic scientists.
Références
[1] Edmond Locard (1877-1966) is the author of a Treatise on Forensic Science (Traité de police scientifique) in seven volumes. This work proposes a methodology for this new science and is still used today as a foundation for all forensic science laboratories worldwide. This treatise includes a study of criminal investigation, proof of identity, fingerprints, and the examination of written documents, among other subjects.
[2] “The eye sees in things only what it looks at, and it only looks at what is already in the mind.” Motto attributed by Lacassagne to Bertillon (Niceforo, 1907)
[3] Crimescope: Multispectral lighting allowing the selection of specific wavelengths for certain traces (fiber, blood, etc.) and thus making them detectable in an environment where they were not visible to the naked eye.
Lieutenant Colonel Pham-Hoai served as head of the biology department at the Criminal Research Institute of the French Gendarmerie (IRCGN) and as a DNA expert at the Court of Appeal of Versailles. Among his most emblematic cases as an expert, he conducted with his former team the genetic analyses related to the violence surrounding the death of Adama Traoré in 2016, and the examination of Nordahl Lelandais’ vehicle in connection with the abduction and murder of Maëlys de Araujo in 2017. Before becoming an expert, he gained recognition for his original contribution to solving the murder of Élodie Kulik. Lieutenant Colonel Pham-Hoai reflects on this initiative, in which familial DNA searching led to the resolution of this long-running investigation.
The context of a criminal case
On the night of January 10–11, 2002, Élodie Kulik, 24 years old, was involved in a road accident near Péronne (Somme). Just before her ordeal, the victim managed to call emergency services. On the audio recording, two male voices can be heard. Élodie Kulik was then raped and killed at a green-waste landfill near the accident site. Her attackers set fire to the upper part of her body. The semi-charred remains were discovered on the morning of January 12, 2002, by a local farmer. The Gendarmerie was assigned the case and began its forensic investigation. A male DNA profile was identified both on the victim’s body and on an object found nearby. This same profile was entered into the national automated DNA database (FNAEG). No match was found for the DNA trace recovered from the crime scene. At the time, in 2002, the database was still in its early stages, with few profiles recorded. Investigators from the Amiens Research Section then launched extensive DNA collection operations from all men of potential interest to the case. Convicted sex offenders not yet in the database, as well as individuals named by anonymous tips or public rumors, were sampled—without success.
In July and August 2002, two more young women, Patricia Leclercq and Christelle Dubuisson, were murdered in the Picardy region. It was established that Patricia Leclercq had been raped before being killed. For these two murders, a different male DNA profile was obtained—again without a match in the FNAEG. This new genetic evidence reinforced the idea that at least two serial killers were operating in Picardy targeting young women. The media frenzy intensified, and public emotion reached a peak in the region. In September 2002, Nicolas Sarkozy, then Minister of the Interior, met with the families of the three victims to express his support. Additional resources were allocated, and the investigators continued collecting DNA samples from all suspects. Through this process, they identified Jean-Paul Leconte as the murderer of Patricia Leclercq and Christelle Dubuisson. However, it was established that Leconte was incarcerated in January 2002 and had not been granted leave. He was therefore ruled out as a suspect in the rape and murder of Élodie Kulik.
Despite the media storm and these unfortunate coincidences, the real challenge for investigators remained above all a human one. The Kulik family had already endured devastating losses. Her parents had lost two children in a car accident in the mid-1970s. Despite this tragedy, the couple had chosen to rebuild their family a few years later, giving birth to Élodie and her brother Fabien. Élodie’s murder became the final blow for her mother, who attempted suicide. Her act led to a vegetative coma that lasted nine years before her death in 2011. Jacky Kulik, Élodie’s father, turned his despair into determination to ensure that his daughter’s murder would be solved. He mobilized support, engaged with the media, and organized white marches to prevent the case from being forgotten. He even offered a reward to anyone who could provide information leading to the arrest of the perpetrators.
Front page of Courrier Picard — Ambush on the departmental road. Credit: France 3 Nord–Pas-de-Calais
Investigators persevered in their efforts, collecting DNA samples from over 5,000 individuals by 2010. None of them matched the DNA profile found at the scene. At the same time, no lead made it possible to identify the second suspect heard on the audio recording, in the absence of his genetic profile. Several investigators and investigating judges succeeded one another on the case. The investigation had reached a dead end.
So how could a young gendarmerie captain, with a scientific background and just beginning his career in judicial police, help?
A Fresh Look at the Élodie Kulik Case file
Assigned to the criminal investigation division in 2009, I arrived with two master’s degrees—one in health engineering and the other in molecular biology. My first three years of service were spent at the Criminal Research Institute of the National Gendarmerie (IRCGN), where I was part of the interministerial committee in charge of the national DNA database (FNAEG). Suffice it to say, I knew little about criminal investigations beyond what I had been taught at the National Gendarmerie Officers’ School. My superior at the time, Colonel Robert Bouche, put me in charge of the property crime division and gave me the additional mission of learning how to lead investigations. Simple at first but quickly grew more complex, like solving an equation. I was clearly not the Institution’s new Sherlock Holmes, but I quickly understood that a well-conducted investigation is nothing more—and nothing less—than a scientific demonstration. The parallel is striking: hypotheses are formed (I suspect Pierre and Paul may be involved in the crime), tested through experiments that generate data (witness statements, physical and technical surveillance provide those data), and the results are interpreted (if my witness testimony and technical surveillance show that Pierre and Paul were indeed present at the crime scene at the time of the offense, can I for all that assert that they are the perpetrators?). By applying scientific reasoning and rigor, I was able to bring objectivity and avoid any form of arbitrariness. This clinical approach to examining the elements of an investigation—regardless of the outcome— allows one to get as close as possible to the factual reality. The hardest part is maintaining some distance from promising early leads that may turn out to be wrong. A good investigator is, in a sense, a scientist without knowing it.
In August 2010, the commander of the Research Section decided to promote me to head of the Crimes Against Persons Division, which handles homicides and narcotics trafficking. That was when I discovered the Kulik case in detail and its scope. Having never taken an interest in this murder before my assignment to Amiens, I read the investigative reports with a fresh perspective, just as Colonel Bouche intended. Scientific reasoning immediately took precedence over any other considerations. First and foremost, I carried out my own work of gathering and synthesizing the data from the case file, avoiding any shortcuts or assumptions.
Judicial evidence seal containing the audio cassette of Élodie Kulik’s call to the Amiens emergency center on January 11, 2003. Credit: Courrier Picard – Frédéric Douchet
As I read through the investigative reports, I realize that all suspects—both the most relevant and the less likely—had been sampled. As soon as a man became a suspect for probable and/or plausible reasons, his genetic profile was obtained and compared with that of the crime scene trace. By 2010, over 5,000 individuals had been tested—the equivalent of a medium-sized town.
All potentially suspicious men, whether they lived or had lived near the crime scene, or were designated through public rumor (in other words, persistent gossip), had their DNA sampled, all without success. What does this teach me about the suspect being sought, and more specifically, about his absence from the DNA sampling operations?
Three explanations could account for his absence:
He had never been involved with the justice system before or after the rape.
He fled to a place where he could never be located and sampled.
He has died since the murder.
Another factor must be taken into account: the extensive media coverage of the case. The press repeatedly made public the fact that a male DNA profile had been recovered at the crime scene. If the suspect is still alive, there is no doubt that he is aware of this information. This gave him a definite advantage—a head start—allowing him to remain on guard. However, this advantage could be compromised by the second suspect, who could at any time denounce him to save himself. Yet since 2002, that has not happened. It seems reasonable to assume that if the second suspect has never come forward, he will continue to stay silent—especially if he is convinced that his own DNA was not found at the crime scene.
In 2010, a conclusion becomes clear to me: the most promising element for identifying the two suspects is the DNA profile left by one of them at the scene. Nevertheless, how can one identify an individual based solely on his genetic profile if it is not in the database—and likely never will be? How can we obtain a last name that could revive the investigation? This is where genetic knowledge, combined with the capabilities of the FNAEG, comes into play.
Storage of biological evidence at the Central Service for the Preservation of Biological Samples (SCPPB), attached to the Institut de Recherche Criminelle de la Gendarmerie Nationale (IRCGN). Credit: PGJN
Familial DNA searching: a new use of genetics in criminal investigation
The DNA profiles recorded in the FNAEG are composed of markers: in 2002, there were 15 of them, with a potential increase to 17. This does not include the marker determining sex. Each marker carries two alleles: one inherited from the father, the other from the mother. Thus, the genetic profile of an individual, defined by 15 markers, contains 30 alleles. Of these 30 alleles, half are identical to those of the individual’s father, and the other half to those of the mother.
When comparing a trace to the genetic profile of an individual, the FNAEG’s comparison engine searches for strict allele matches. In other words, in the case of a 15-marker individual, all 30 alleles must be identical to those of the trace for the database to return a hit (commonly referred to by experts as a “match”) to the investigator. If not, the search is deemed unsuccessful. Yet there are cases where partial correspondences may be of value: those in which the parent of a trace donor is sought.
Indeed, if the suspect is not in the database, perhaps their parents or children are. These relatives could lead investigators to the suspect by providing a surname. From there, the suspect’s family tree can be reconstructed using civil registry records. The method is straightforward: if the suspect’s parent is in the database, the search engine should return all individuals whose profiles share 50% of their alleles with the crime scene trace. Complementary analyses such as paternity or maternity tests can then definitively confirm the kinship link between the individual and the trace.
As this idea seemed coherent, I began researching whether it had already been implemented abroad. Following a scientific approach, I conducted a literature review. I humbly assumed that other scientists abroad must have had the same idea, implemented it, and published their findings. Their experience—whether successful or not—could help me save time. This search led me to a case report published in the renowned journal Science. The article described the case of the “Grim Sleeper,” a serial killer responsible for at least eleven murders of young women in California between 1985 and 2010. Although he had left his DNA at multiple crime scenes, he had always eluded law enforcement and was never entered into the database. North American experts used the same approach I had imagined and successfully identified his son whose genetic profile was registered for prior offenses. The article also mentioned other U.S. states using this technique. At this stage of my research, I was convinced that the FNAEG must already be using such searches, albeit on an exceptional basis. To my great surprise, when I contacted the database representatives, I learned that this scenario was not provided for.
The publication of familial DNA searching in a major scientific journal reassured me of the validity of my approach. Thanks to contacts from my previous posting, I submitted my proposal to the Directorate of Criminal Affairs and Pardons at the Ministry of Justice. Their response confirmed that it would be a first in France: the FNAEG had never been envisaged in this way. Nothing prohibited such a search, but nothing explicitly allowed it either. The immediate question was whether the technique would be legally valid if it led to the identification of one of Élodie Kulik’s attackers. A year of debate followed to ensure that the investigation would not be compromised by this new method. The decision finally came in 2011: we were authorized to use the technique. If successful, it would not constitute grounds for procedural nullity. In the background, it was even envisaged that the method could be extended to a broader range of cases.
Once authorized, the request was submitted to search the FNAEG for all individuals sharing half their alleles with the crime scene trace. As with our North American counterparts, the gamble paid off and yielded a second surprise—this time a fortunate one: the suspect’s father was in the database. A paternity test based on comparing the Y chromosome in the trace and that of the identified individual confirmed that they belonged to the same paternal line. With the surname now identified, we reconstructed the suspect’s family tree. We traced it back to his eldest son, the likely source of the trace. Then came a third, less pleasant surprise: the suspect had died in 2003 in a road accident, just one year after the crime. After ensuring that no other family member could be involved, his body was exhumed in early 2012. The analysis confirmed that his genetic profile matched the crime scene trace.
The suspect’s death shortly after the events explained his absence during DNA collection operations from 2002 to 2010. The experiments permitted to validate the hypotheses. Even if difficulties lay ahead, I knew that the case would eventually be solved. Once investigators have a lead—and even more so a name—they pursue it to the end. Extensive work was carried out to reconstruct the suspect’s family and social environment prior to his death. That’s how, by mid-2012, the second suspect was identified. He was later confirmed by voice recognition from the emergency call made by Élodie Kulik on the night of her death. Tried at first instance in December 2019 and again on appeal in July 2021, he was sentenced to 30 years in prison for the rape and murder of Élodie Kulik.
When people ask how I came up with the idea of searching for a relative of the suspect in the FNAEG—an idea some consider brilliant, though it is in fact very simple—I always give the same answer: there’s nothing extraordinary in what I did. It was scientific reasoning combined with investigative experience. Hypotheses were formulated, then tested using investigative tools. Results were considered with appropriate distance. Discussions were held with more experienced gendarmes—because collective reflection is always better than facing a difficult result alone. This is something any scientist or any individual with intellectual rigor and logic could do.
The similarity between identical twins is not only physical. They also share the same genetic heritage, which can undermine the famous DNA evidence. But perhaps not for much longer…
A recent case illustrates the challenge of judging a criminal matter involving twins. On March 17, 2021, the Assize Court of Val-d’Oise in Pontoise heard the case of two twin brothers charged with three attempted murders. Acquitted of the first two charges, they were nonetheless both sentenced to twelve years in prison for the third. A surprising decision, but one justified by the impossibility, in the first two cases, of determining with certainty to whom the DNA traces found on a handgun actually belonged.
This case is reminiscent of the Gomis brothers affair, involving a series of rapes and attempted rapes in the Marseille area in 2013. Unable to distinguish them based on their DNA, the police initially charged the wrong twin before obtaining a confession from the actual perpetrator.
Alike, but not 100% identical.
Identical twins, also known as monozygotic twins—originating from the division of the same egg fertilized by the same sperm cell—share the same genetic heritage. This makes it extremely difficult to differentiate them on the basis of DNA, which in recent years has become the gold standard of scientific evidence in criminal investigations. DNA analyses focus on tiny non-coding regions of the genome, which vary from one individual to another but are identical in true twins.This genetic challenge, however, may soon be overcome. In a study of 387 pairs of twins published on January 7, 2021 in the journal Genetics, Icelandic scientists highlighted the existence of early genetic mutations occurring during gestation, at the time of cell division. These sometimes minor alterations help explain physical differences as well as variations in susceptibility to certain diseases.
Distinct fingerprints.
In the future, advances in laboratory sequencing techniques may allow twins to be distinguished by their DNA. Until that technological leap is achieved, forensic science can still rely on fingerprint analysis. Every individual possesses unique fingerprints, with the statistical probability of sharing them with another person estimated at 1 in 64 billion—so low as to be practically impossible.
Contrary to common belief, twins are no exception to this rule. While DNA plays a fundamental role in shaping fingerprints, many other factors influence their formation. Developed in utero between the thirteenth and twentieth week of gestation, fingerprints are subject to a range of environmental ‘stresses’: pressure against the uterine walls, friction within the amniotic fluid or against the umbilical cord, thumb sucking by the fetus. According to some studies, maternal behavior may also affect fingerprint patterns: exposure to toxic agents (alcohol, drugs), certain medications, viral or bacterial infections, or even psychological stress during pregnancy can all increase the likelihood of alterations. After birth, accidents, skin diseases, or medical treatments may further modify the detail of the ridge patterns.
These are valuable indicators that forensic science can use, when confronted with a criminal case, to resolve the mystery of twin identity.
Forensic police has long been accustomed to tracking DNA at crime scenes, most often found in bodily fluids and hair. A recent discovery by two scientific teams has now demonstrated that this genetic signature can also be found in the air.
As is often the case with scientific breakthroughs, it all began with research far removed from criminalistics. In early 2021, researchers from the University of York in England and the University of Copenhagen in Denmark installed air-sampling devices equipped with filters in two European zoos to collect air samples and analyze their composition. The initial goal was to determine whether this method could be used to identify the animal species present in a natural habitat, monitor them to improve protection, and thus achieve highly accurate tracking of endangered species.
The results of the sequencing went far beyond expectations: in both cases, the scientists detected not only the DNA of numerous animal species but also human genetic material from the individuals conducting the experiment. A first of its kind—and a development that promises to further advance forensic investigation techniques.
Human DNA: a marker unique to each individual.
It was only in the 1980s that criminal investigations began incorporating the search for DNA traces at crime scenes. This breakthrough was pioneered by Alec Jeffreys, a British researcher at the University of Leicester. Once again, the aim of his research was far removed from forensic science: his team was primarily studying the hereditary transmission of certain genetic diseases. Along the way, however, they discovered that portions of the genome’s DNA are unique to each individual. This discovery led, in 1985, to its first practical application. Called upon by police investigating the murder of two young girls, Jeffreys’ laboratory demonstrated—through semen traces collected at the crime scene—that both killings had indeed been committed by the same individual.
DNA in the air: a decisive breakthrough.
Advances in sampling and analysis techniques, along with the launch in 2000 of the French National Automated DNA Database (FNAEG), which today contains nearly 3.5 million genetic profiles, have already revolutionized investigative methods. It is now possible to detect and sequence DNA from even the tiniest traces left behind by an individual—whether perpetrator or victim. This includes blood, semen, or sweat, as well as hair with its root attached. In the absence of a hair bulb, mitochondrial DNA (inherited exclusively from the maternal line) is targeted.
The ability to capture DNA suspended in the air and compare it to that of potential suspects or to entries in existing databases opens up entirely new perspectives for solving the most complex criminal cases.
For investigators, locating the bodies of missing persons buried in natural environments is a complex—if not impossible—task. In the future, however, trees themselves may help. Here’s how.
For now, it remains a theory, but it comes from the highly respected Forensic Anthropology Center at the University of Tennessee (USA), which in 1980 established the first « Body Farm ». This center has specialized in a field of study that may seem somewhat macabre but is of great value to criminal investigations: examining how human remains decompose depending on the environment in which they are placed, as well as under different climatic conditions (cold, heat, humidity, etc.). Researchers are particularly focused on how the human microbiome (the community of microorganisms and their genes) reacts after death.
Monitoring leaf color.
When a body decomposes in a natural environment, it alters the composition of the soil. In the absence of the immune responses that occur in a living organism, bacteria multiply and mix with the microorganisms present in the earth. From this observation, researchers developed the following hypothesis: could these changes in the soil also affect the trees that draw nutrients from it? And if so, could such changes be detected in the color and reflectance (the proportion of light reflected by a surface) of their leaves?
Nitrogen, a visible marker.
Among the chemical components likely to affect vegetation, researchers highlight nitrogen, present in large quantities in the human body and also a common ingredient in fertilizers used to boost plant growth. Plants exposed to it produce more chlorophyll, and their leaves become greener—changes that could become a factor in visual detection.
However, other interactions complicate these observations: for example, the presence in decomposing bodies of certain metals or traces of pharmaceuticals. More simply, the natural ecosystem in which the body is deposited also comes into play: necrophagous insects, scavengers, animal droppings…
Lastly, there remains the challenge of distinguishing the effects of human decomposition from that of other large mammals—deer, wolves, bears, cattle, and so on. In both wild environments and agricultural lands, animals die and decompose, and at present there are no comparative studies available to differentiate between these various microbiomes.
Cadaveric decomposition and colonization by necrophagous insects.
Scanning the area with a drone.
In the face of these many challenges, the Forensic Anthropology Center at the University of Tennessee proceeds step by step. First, researchers placed ‘donors’ (individuals who had donated their bodies for research purposes) in designated plots of land in order to observe how vegetation responded to this macabre exposure. Soil that had been in contact with human decomposition was then transferred to a greenhouse to more closely monitor the plants and their modifications.
These examinations are carried out using hyperspectral imaging, which highlights chlorophyll-induced fluorescence in leaves—a technology already used to detect cannabis and poppy fields from the air.
If this study proves successful, it could revolutionize the search for missing persons. With drones and imaging technology, it would become possible to scan large or hard-to-access areas and detect changes linked to decomposition processes nearby. This would save valuable time for law enforcement and give families hope of finding closure.
From as far back as crime has existed, the offender’s natural reflex has been to conceal their traces in an attempt to escape justice. That said, to succeed, the traces of their action or passage must first be visible to the naked eye…
“No one can act with the intensity implied by criminal behaviour without leaving multiple marks of their passage. Sometimes the offender has left at the scene the marks of their activity; sometimes, by the opposite action, they have carried on their person or on their clothing the evidence of their presence or of their act.” — Edmond LOCARD, L’enquête criminelle et les méthodes scientifiques, Flammarion, Paris, 1920.
Microtraces: a very discreet clue
As Edmond LOCARD explained in his treatise on criminalistics, the perpetrator leaves traces of themselves and of their environment on the victim and at the crime scene and, conversely, takes away traces of their action. A criminal investigation therefore relies in part on the material traces found at the site of an offence or on a crime scene. To that end, investigators and forensic scientists methodologically gather traces and clues.
Over the past two decades, television series have broadly popularized the importance of collecting traces at a crime scene or from a suspect. The possibilities for exploiting those traces to solve an investigation are now well known to the general public. Television and the internet have doubtless also contributed to educating future offenders by informing them about the types of traces that can incriminate them.
Yet one type of trace remains relatively confidential today: the infinitesimally small. This world, where the human eye reaches its limits, is also populated by exploitable traces known as “microtraces.” Their dimensions are generally smaller than a millimetre and escape our perception. The only challenge is to be able to collect them without seeing them — by means of systematic sampling — in order to exploit them later.
A single cell from the human body contains all the material necessary to establish our genetic profile — in other words, our DNA. It is therefore not necessary for an offender to wound and bleed — or to deposit other biological fluids (notably saliva or semen) — to leave their DNA at a crime scene. Indeed, any contact with the victim or manipulation of objects in the victim’s environment can transfer a few skin cells and potentially allow recovery of that individual’s DNA. In the absence of direct contact, microscopic projections of saliva or blood can also lead to DNA identification.
A clump of hair torn from the victim’s hand is no longer the type of evidence an offender will likely leave behind. However, a victim’s clothing—or, in the case of sexual assault, their undergarments—may retain microscopic hairs or hair fragments, also capable of leading to the offender’s DNA.
When crimes occur outdoors, nature can also aid justice through microscopic debris of minerals or plants. Such traces may be recovered, for example, from the soles of shoes, clothing, or even the pockets of an offender. These microtraces may indicate the nature of the soil or vegetation at the crime scene, or the location where the victim may have been moved after the incident.
Without being exhaustive, another type of biological microtrace—diatoms—may be found in a victim’s lungs and assist in determining whether the victim drowned in the waters where they were discovered (accidental hypothesis) or whether the scene was staged, for instance, with prior drowning in a water supply system. Diatoms, a type of unicellular microalgae, may also differ between the waters at the discovery site and the waters where the drowning actually occurred, thereby redirecting the investigation to the original crime scene.
Microtraces of chemical origin
Firearms are frequently used or displayed in criminal acts. Handling or discharging a firearm contaminates the offender’s hands, face, and clothing with gunshot residues. These residues are microscopic particles with distinctive morphology and chemical composition, although the latter can vary depending on the ammunition and weapon involved. Clothing is also particularly useful for revealing criminal contacts. Indeed, friction between two textiles in contact leads to the transfer of microscopic entities: textile fibres. These fibres, the basic components used to produce textile threads and, ultimately, garments, are also present on the surface of clothing, where they may be exchanged through friction. Such transfers can be even more pronounced when the interaction between victim and offender is violent. A victim’s clothing therefore harbours textile fibre microtraces originating from the offender’s garments, particularly in areas of concentrated contact, such as the neck in a case of strangulation. In line with the principles established by Edmond LOCARD, the offender will also carry away microtraces of fibres originating from the victim’s clothing.
A hit-and-run accident can often have serious consequences for the injured victim, particularly when the victim is a vulnerable road user such as a pedestrian or cyclist. In the absence of video surveillance and automotive debris at the accident site, microscopic traces of automotive paint may be recovered from the victim’s clothing. Their analysis can lead to the identification of a make—or even a model—of vehicle to be traced by the police. Once a suspect vehicle has been located, a formal comparison may be made with the paint from the damaged areas. In most cases, such comparison remains possible even if the vehicle has been repaired in the meantime.
Microtraces: a broad subject
Microtraces are as diverse and varied as the biological or chemical materials capable of dispersing or fragmenting into microscopic evidence. The aim of this article is not to be exhaustive; the examples mentioned here briefly illustrate the most common microtraces encountered in criminal investigations. Each type of microtrace requires specific collection methods by trained personnel and specialized analytical techniques in forensic laboratories—too detailed to be explained in this general overview. More targeted articles will be better suited to detail the forensic value of each type of microtrace in criminal investigation.
The identification of human remains belonging to missing persons continues to be a challenging process in forensic genetics. When an unidentified body or human remains are discovered, the most reliable method of identification is a comparison between the post-mortem DNA profile (obtained from biological tissue samples collected during the autopsy) and the ante-mortem DNA profile (typically obtained from the missing person’s personal belongings or from a prior medical sample) [1].
Some countries have established national missing persons identification programs using DNA analysis, which are highly effective when both the disappearance of individuals and the discovery of unidentified human remains occur within the same country. However, many investigations remain unsolved even after all domestic leads have been pursued.
International cooperation in missing persons investigations is therefore strongly recommended in light of increasing global migration, the growing impact of transnational crime and human trafficking, the vulnerability of migrants and refugees, and their heightened risk of becoming victims of criminal acts.
INTERPOL, the world’s largest international police organization, is mandated to take part in international investigations, including those involving missing persons, by connecting its 195 member countries. The Organization works primarily with national law enforcement agencies through the INTERPOL National Central Bureau (NCB) present in each country, but it can also cooperate with other international entities involved in disaster victim identification and missing persons cases. INTERPOL provides the legal framework and technical infrastructure for the secure exchange of information and access to its 19 databases, thereby enabling police worldwide to collaborate (Figure 1).
Created in 2002, INTERPOL’s DNA database currently contains more than 250,000 profiles provided by 86 member countries. National Central Bureaus and international entities can submit a DNA profile obtained from a suspect or convicted offender, from crime scenes, from missing persons, and from unidentified human remains, with an automated search result provided within minutes. No nominal data is attached to the profile, and member countries retain ownership of their information, in accordance with INTERPOL’s data processing rules. Countries can also choose with whom they wish to make their data available for comparison. INTERPOL’s DNA database has enabled investigators worldwide to link offenders to different types of crimes, including rape, murder, and armed robbery, as well as to formally identify missing persons found deceased outside their national borders from which they had been reported missing.
However, in many cases, direct DNA matches are not possible because ante-mortem DNA profiles are either unavailable or insufficient to confirm the identity of the missing person. This is often due to the inability to retrieve personal items (e.g., a toothbrush belonging to the missing person) or to access medical records that might contain relevant biological information. Consequently, in most cases, ante-mortem DNA data can only be obtained through the donation of biological samples by relatives genetically related to the missing person to the requesting authorities.
While most laboratories have the capacity and experience to perform relatively simple kinship tests, such as paternity testing, the evaluation of more complex kinship scenarios is far more challenging [2]. Specialized computer software is often required to compare ante-mortem and post-mortem data and to conduct complex kinship calculations using large DNA profile datasets. This software computes likelihood ratios (LR), which provide the optimal basis for statistical decision-making, regardless of whether or not there is an assumption about prior probabilities [3]. By using allele frequencies specific to the reference population to which the missing person belongs, the probability that a missing person could be part of a pedigree composed of family members whose DNA is available (e.g., parent, child, or sibling of the missing person) is assessed by comparing two hypotheses, H1 and H2. H1 supports that the individual belongs to the pedigree under study, while H2 supports that they are not related [2]. Although it is possible to implement this method within a national framework (kinship searching is used in several countries, including France, for example) where both the missing person and the unidentified human remains are reported in the same country, many challenges had to be addressed before applying this method in an international setting.
INTERPOL has addressed these challenges and, in June 2021, officially launched its 19th database, I-Familia, dedicated to the global identification of missing persons through DNA-based kinship analysis (Figure 2).
Figure 2: The DNA comparison process for missing persons investigations using INTERPOL’s DNA database and I-Familia. Credits: INTERPOL.
I-Familia is an innovative, free-of-charge service available to INTERPOL’s 195 member countries to help identify potential biological relationships between the DNA profiles of relatives of missing persons and unidentified human remains worldwide. I-Familia is characterized by three components. First, a dedicated DNA database that hosts the anonymous DNA profiles of biological relatives of missing persons and of unidentified human remains. This is a stand-alone database, separate from other INTERPOL databases containing criminal data. Second, the advanced BONAPARTE software [4], which is used to manage likelihood ratio calculations for any family pedigree using available DNA data (autosomal STR profiles, Y-STR, or mitochondrial DNA) against all DNA profiles from unidentified human remains. Third, scientifically validated interpretation rules [5] to assist users in interpreting statistical results and in the decision-making process that leads to either the rejection or the declaration of a potential biological relationship.
The statistical evaluation of whether a DNA profile belongs to a genetic pedigree requires the use of allele frequencies from a reference population. Since information on the genetic origin of individuals whose DNA is being studied is often missing or inaccurately reported, I-Familia enables likelihood ratio calculations using global allele frequencies [6], together with a correction factor to account for the degree of allele relatedness due to shared ancestry. To streamline the decision-making process and the assessment of potential biological relationships, extensive pedigree simulations were performed to accurately determine optimal likelihood ratio thresholds. Based on the ten most common scenarios encountered in missing persons investigations (depending on the availability of DNA profiles from biological relatives such as parents, children, or siblings) and the number of STR genetic markers comparable between profiles (ranging from 6 to 24 markers), likelihood ratio thresholds help limit the reporting of false positives while minimizing the rejection of false negatives. Interpretation tables, specifically designed to reflect the expected number of coincidental matches for each type of comparison, are extremely useful in determining the most appropriate decision (to assess the match, to reject it, or to request additional DNA information).
When the evidential value of the DNA study is sufficient and the ante-mortem and post-mortem data are compatible, a potential biological relationship report is sent to both data sources, which can then cooperate bilaterally to confirm the identification using their national procedures.
I-Familia has already enabled the identification of missing persons whose bodies were found in countries other than where they had been reported missing. The first confirmed match was made between the DNA profiles of the children of an Italian missing person and that of a body recovered in the Adriatic Sea by Croatian police in 2004, closing a case that had remained unresolved for nearly 16 years.
By the end of 2021, more than 12,000 active Yellow Notices—INTERPOL’s international police alerts for missing persons—had been issued by the General Secretariat, highlighting the need for greater international cooperation. I-Familia is a humanitarian tool that, thanks to INTERPOL’s global reach, opens up vast new possibilities for identifying missing persons and providing answers to families.
For further information on I-Familia, please consult the I-Familia brochure [7].
References:
[1] Recommendations on the Use of DNA for the Identification of Missing Persons and Unidentified Human Remains by the INTERPOL DNA Monitoring Expert Group, (2017). http://www.interpol.int.
[2] M.D. Coble, J. Buckleton, J.M. Butler, T. Egeland, R. Fimmers, P. Gill, L. Gusmão, B. Guttman, M. Krawczak, N. Morling, W. Parson, N. Pinto, P.M. Schneider, S.T. Sherry, S. Willuweit, M. Prinz, DNA Commission of the International Society for Forensic Genetics: Recommendations on the validation of software programs performing biostatistical calculations for forensic genetics applications, Forensic Sci. Int. Genet. 25 (2016) 191–197. https://doi.org/10.1016/j.fsigen.2016.09.002.
[3] A. Collins, N.E. Morton, Likelihood ratios for DNA identification., Proc. Natl. Acad. Sci. 91 (1994) 6007–6011. https://doi.org/10.1073/pnas.91.13.6007.
[5] FX. Laurent, A. Fischer, R. Oldt, S. Kanthaswamy, J. Buckleton, S. Hitchin, Streamlining the decision-making process for international DNA kinship matching using worldwide allele frequencies and tailored cutoff log10LR thresholds, Forensic Sci. Int. Genet. 56 (2021). https://doi.org/10.1016/j.fsigen.2021.102634.
[6] J. Buckleton, J. Curran, J. Goudet, D. Taylor, A. Thiery, B.S. Weir, Population-specific F values for forensic STR markers: A worldwide survey, Forensic Sci. Int. Genet. 23 (2016) 91–100. https://doi.org/10.1016/j.fsigen.2016.03.004.
The olfactory trace can be defined as the identification of an individual by their scent. Just like fingerprints, genetic profiles, and now digital footprints, the olfactory trace could, over time, be used as a specific marker of an individual.
The olfactory trace originates from the odor emitted by a human being, which may either be left on a surface following contact, or remain suspended and carried in the air after the person has passed by. Although the notion of an odor trace is not new, it was not until the end of the 20th century that the feasibility and relevance of collecting such traces—initially not obvious (unlike a bloodstain, a flammable liquid spill, or a ballistic impact, which are “visible”)—were demonstrated. Advances in collection materials (polymers, fabrics, etc.) also made it possible to collect and preserve these traces. At the same time, analytical developments (notably chromatography) made it possible to better detect these traces and to gain a more accurate understanding of their composition.
It is now possible to collect such traces at a crime scene, as well as directly from individuals themselves, for comparison purposes. The so-called “odorology” or “forensic scent identification” techniques using dogs are based on this comparison between an odor collected at a scene (odor trace) and a bodily odor taken directly from an individual (direct odor).
Odor is a complex combination of several hundred molecules. Among them, one can distinguish a so-called primary component, consisting of a genetically determined static part that is thought to remain stable in an individual over time. Added to this are more variable components: a secondary odor, influenced by parameters such as physical or psychological activity, diet, and environment; and a tertiary odor, derived from cosmetics and other exogenous compounds in general.
Despite this complexity, the effectiveness of dogs in locating missing persons or following tracks is well established. However, this approach will always face limitations in the formal identification of an individual who is no longer present at a given location and time. These limitations are due, so far, to the lack of knowledge about how the canine sense of smell works, and particularly about which molecules are involved in recognizing an individual—an aspect that remains a mystery, even in the scientific literature.
The lack of information about the trace itself and about the odor discrimination process carried out by dogs during tracking is a real obstacle and diminishes the evidential strength of the method.
Moreover, the potential bias introduced by the line-up procedure itself, as well as the question of how to interpret a dog’s failure to mark (absence of trace or failure of detection), also arise.
These observations have led specialists at the IRCGN to consider, alongside canine methods, alternative approaches involving collection techniques, chemical analyses, and statistical processing, in order to exploit this promising trace by other means.
With a view to formal identification in criminal proceedings, the use of two orthogonal techniques (canine teams and laboratory analyses) that ultimately converge on the same individual would considerably strengthen the evidential value of the trace.
In the long run, a “laboratory-based” approach would thus provide genuine support for dog-based identifications. Indeed, a dog’s marking could be confirmed in the laboratory, and in cases where no marking occurs due to a partial or degraded trace, laboratory classification could still help guide investigators and magistrates in their inquiries.
Chromatographie tridimensionnelle d’une odeur corporelle – Crédits : PJGN -IRCGN
Analyse par thermodésorption couplé à la chromatographie gazeuse et à la spectrométrie de masse. Crédits : PJGN – IRCGN
The “Olfactory Trace” project, led by the IRCGN, is built on an evolutionary design principle. It simultaneously involves work on sample collection—through the development of methods and tools that can be easily used in the field (including a patented sampling pump)—the use of advanced analytical tools such as comprehensive two-dimensional gas chromatography coupled with mass spectrometry, as well as data processing techniques (computational and statistical). The IRCGN’s aim is to provide investigators with a solution to classify, and even individualize, in order to increase the evidential value of the information provided by the dog.
This research project may also address issues beyond the forensic field, since it involves the identification of chemical molecules secreted by the human body, some of which are of interest to the medical community, particularly for diagnostic purposes.
For example, the “KDog COV” project, led by the Institut Curie, is a human-based study aimed at analyzing human odor to detect potential chemical markers of breast cancer using analytical chemistry techniques. The objective of this research program is to develop a simple, low-cost, and non-invasive screening method for breast cancer. Analyses are carried out in partnership with the IRCGN, which has already developed methods for sampling and analyzing human odor in the forensic field.
Reference of this work:
[1] V. Cuzuel, G. Cognon, I. Rivals, C. Sauleau, F. Heulard, D. Thiébaut, J. Vial, Origin, analytical characterization and use of human odor in forensics, J. Forensic Sci. 62 (2017) 330–350. doi:10.1111/1556-4029.13394.
[2] V. Cuzuel, E. Portas, G. Cognon, I. Rivals, F. Heulard, D. Thiébaut, J. Vial, Sampling method development and optimization in view of human hand odor analysis by thermal desorption coupled with gas chromatography and mass spectrometry., Anal. Bioanal. Chem. 409 (2017) 5113–5124. doi:10.1007/s00216-017-0458-8.
[3] V. Cuzuel, A. Sizun, G. Cognon, I. Rivals, F. Heulard, D. Thiébaut, J. Vial, Human odor and forensics. Optimization of a comprehensive two-dimensional gas chromatography method based on orthogonality: How not to choose between criteria, J. Chromatogr. A. 1536 (2017) 58–66. doi:10.1016/j.chroma.2017.08.060.
[4] V. Cuzuel, G. Cognon, D. Thiebaut, I. Rivals, E. Portas, A. Sizun, F. Heulard, Reconnaître un Suspect grâce à son Odeur : du Chien aux Outils Analytiques, Spectra Analyse, 318 (2017) 38–43.
[5] V. Cuzuel, R. Leconte, G. Cognon, D. Thiébaut, J. Vial, C. Sauleau, I. Rivals, Human odor and forensics: Towards Bayesian suspect identification using GC × GC–MS characterization of hand odor, J. Chromatogr. B Anal. Technol. Biomed. Life Sci. 1092 (2018) 379–385. doi:10.1016/j.jchromb.2018.06.018.
[6] I. Rivals, C. Sautier, G. Cognon, V. Cuzuel, Evaluation of distance‐based approaches for forensic comparison: Application to hand odor evidence, J. Forensic Sci. (2021) 1556-4029.14818. doi:10.1111/1556-4029.14818.
[7] M. Leemans, I. Fromantin, P. Bauër, V. Cuzuel, E. Audureau, Volatile organic compounds analysis as a potential novel screening tool for breast cancer: a systematic review (submitted)
