The signatures of microorganisms and of human and environmental biomes can now be used to provide evidence in legal cases.

The microorganisms with which we share our world go largely unnoticed. We are, however, beginning to be able to exploit their apparently silent presence as witnesses to events that are of legal concern. This information can be used to link forensic samples to criminal events and even perpetrators. Once dead, our bodies are rapidly colonised, internally and externally. The progress of these events can be charted to inform how long and even by what means a person has died. A small number of microbial species could actually be the cause of such deaths as a result of biocrime or bioterrorism. The procedures and techniques to respond to such attacks have matured in the last 20 years. The capability now exists to identify malicious intent, characterise the threat agent to isolate level and potentially link it to perpetrators with a high level of confidence.

HIV legal precedent useful for microbial forensics.

The field of microbial forensics was formalized because of the need for attribution in events where a bioweapon has been used. Microbial forensics has its origins in traditional forensics, microbiology, and epidemiology. Microbial forensics can be defined as a scientific discipline dedicated to analyzing evidence for attribution purposes from a bioterrorism act, biocrime, hoax, or inadvertent microorganism/toxin release. This is a very challenging task, since there are myriad microorganisms that can pose a threat, and analytical methods need to be used reliably. The Scientific Working Group on Microbial Genetics and Forensics (SWGMGF) has addressed some quality assurance and control issues, and particularly validation criteria (focusing on preliminary validation) due to the dynamic nature of evolving investigations. Unique identification of a microorganism may never be possible. Yet, qualitative and/or quantitative assessments of the evidence can be made. One approach to provide direction on gaps in the microbial forensics effort is to perform an end-to-end retrospective analysis of past cases. As an example, the case of a gastroenterologist who was accused of second degree attempted murder of his paramour using HIV as the weapon was reviewed. The scientific evaluation involves epidemiology, molecular biology, phylogenetics, and legal deliberations.