U.S. flag

An official website of the United States government, Department of Justice.

The Evidence We Leave Behind (Part 2)

NCJ Number
Date Published
June 2022

In this “Justice Today” podcast sponsored by the National Institute of Justice (NIJ), Gregory Dutton, a physical scientist at NIJ, and science writer Jim Dawson continue their conversation on the microbiome, i.e., what it is, how it applies to forensics, and the evolution of its role in forensic science; online access is also provided to Part 1 of this interview.




 Dutton notes that a suspect’s biological material, such as biological fluids or skin, may be left at a crime scene and can be collected for subsequent DNA analysis. In the absence of or problems with such biological evidence, a suspect may leave a lot of bacteria or microbes that may be useful as a means of suspect identification. In analyzing bacterial microbiome, a gene that all bacteria have is 16S ribosomal RNA. Some are the same across all species, and some regions are variable; there is a specific place to look in a bacterial genome to classify the kind of bacteria. The sequences in the 16S rRNA region are characteristics of the type and species of bacteria. This is done to identify groups and species of bacteria. The more recent research in trace microbiome is looking for specific species that may provide more ability to differentiate between individuals based on the bacteria groups carried by their bodies. The types of bacteria that live on a particular person are adapted to the environment in which that individual lives, providing a set of bacteria distinctive to that person’s environment or lifestyle. The interview considers where microbiome science is headed, including how an individual’s presence at a crime scene may deposit microbiomes at the scene and how microbiomes can be collected and analyzed.

Date Published: June 1, 2022