Bedbugs: a new weapon for forensic science?

Malaysian researchers have explored the potential of tropical bedbugs, Cimex hemipterus, as a new source of human DNA in forensic investigations. Typically overlooked in crime scene analyses due to the absence of visible traces, these insects may nevertheless carry, within their digestive tract, the DNA of the last human host they fed on. The study aimed to determine whether—and for how long—a usable human DNA profile could be extracted from the blood meal content of bedbugs, focusing on two key forensic genetic markers: STRs (Short Tandem Repeats) and SNPs (Single Nucleotide Polymorphisms).

Methodology and results

Laboratory-reared bedbug colonies were fed on human volunteers and subsequently sacrificed at different intervals (0, 5, 14, 30, and 45 days after feeding). DNA was extracted and subjected to STR and SNP analyses following standard forensic protocols. The results were conclusive: complete STR and SNP profiles could only be obtained on the day of feeding (day 0), while partial, though still informative, profiles remained detectable up to 45 days post-feeding. The SNP data were interpreted using the HIrisPlex-S system, allowing phenotype predictions (eye, skin, and hair colour) even from partial genetic information. Moreover, field-collected bedbugs confirmed the feasibility of STR profiling, occasionally revealing mixed DNA profiles—potentially indicating feeding from multiple human hosts.

Legal implications and future prospects

These results open up a new avenue for forensic science: when traditional biological traces have disappeared or been cleaned away, bedbugs could remain at the scene and serve as reliable micro-reservoirs of human DNA, enabling investigators to identify individuals who were present or to establish a timeline of movements. However, several limitations must be taken into account. First, the analyses are time-consuming and require a rigorous protocol. The DNA profile becomes partial after a few days, and some loci are no longer detectable. Moreover, when an insect has fed on multiple individuals, mixed genetic signals can occur, making interpretation more complex.

The authors emphasize the need to validate these findings on a broader range of samples, including more human donors and various commercial STR/SNP kits. Controlled in situ tests on simulated crime scenes would also be useful to confirm the robustness of the method—particularly in comparison with other insects or biological intermediaries considered in forensic entomology.

Conclusion

In summary, this study demonstrates that human DNA preserved in the stomach of tropical bedbugs can be exploited for up to 45 days after feeding through STR and SNP analysis. Although a complete genetic profile can only be obtained immediately after feeding, these insects represent an innovative and promising resource for forensic science, especially in situations where conventional methods fail. Nevertheless, the approach requires strict protocols, further validation studies, and realistic crime-scene modelling before it can be used in judicial proceedings. Additional research will determine how this strategy can be integrated into the growing toolkit of forensic investigators and scientists.

Sources :

• Kamal, M. M. et al. (2023) – Human profiling from STR and SNP analysis of tropical bed bug (Cimex hemipterus) for forensic science, Scientific Reports, 13(1), 1173.
• Chaitanya, L. et al. (2018) – HIrisPlex-S system for eye, hair and skin colour prediction from DNA, Forensic Science International: Genetics, 35, 123–134.
• Asia News Network (2023) – Malaysian scientists discover bed bugs can play role in forensic investigations, Read full article.
• ResearchGate – Publication originale – Human profiling from STR and SNP analysis of tropical bed bug Cimex hemipterus for forensic science, Read full article.