Microbial Forensics: The Biggest Thing Since DNA?

Abstract

We live in a microbial cloud. Our bodies are home to between two and six pounds of microbial life-cells that do not share our DNA but replicate and live on our skin and hair, in our colons, between our toes, and in our mouths. Although some microbes are pathogenic, most are benign; and many are beneficial. For instance, the microbes in our colons are essential to proper digestion. We now realize that bacteria aid in the development of the immune system, fight off pathogens, and regulate our metabolism. Understandably, scientists are paying increasing attention to the human microbiome.

The growing appreciation of human micobiome is already having a profound effect on the practice of medicine. By way of example, physicians are now using fecal transplants to “infect” a patient with healthy intestinal bacteria to treat microbe-related diseases. The new insights into the microbial cloud also have forensic implications. As this article explains, microbial analysis can potentially be employed in: –tracing infections to a source; –more broadly, making personal identifications; –improving estimates of post-mortem interval; –identifying types of body fluids; and –soil mapping.

Some Spanish and American courts have already admitted expert testimony based on microbial forensic techniques. However, it is far too early to proclaim that the recognition of the importance of the human microbiome is the second coming of DNA. Yet, it is virtually inevitable that in the future litigators will encounter such testimony in court. The purpose of this article is two-fold. First, the article will help generally familiarize members of the American legal profession with the new field of microbial forensics. Secondly, we hope that that familiarity will stimulate a discussion of the question whether any of the foreseeable applications of microbial forensics have sufficient empirical validation to satisfy Daubert and produce admissible evidence.