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Solving Crimes with Soil Bacteria

NCJ Number
Date Published
September 2017
3 pages
This report summarizes the NIJ-funded project of molecular geneticist and forensic scientist David Foran, who has worked with his students at Michigan State University to examine the distinctive DNA of the bacteria found in soil as legitimate evidence in criminal cases.
The research goal is to develop a "soil individualization technique" that enables a forensic expert to produce objective, statistical data that conclusively show soil distinctive to a crime scene can be matched to soil on a tool, clothing, or other item possessed by a suspect. This work has included DNA analysis of the millions or billions of bacteria found in soil samples taken from woodlands, fields, backyards, and dirt roads. Some students even collected slaughterhouse blood to study the bacterial changes caused when blood mixes with soil. Using next-generation sequencing (NGS) of bacterial DNA, Foran has used supervised classification techniques to classify the bacterial composition of a soil sample and give values that are, according to Foran, "completely objective." The statistical data from bacterial analysis meet the Daubert standard on the admissibility of scientific testimony. The individualization of bacterial populations in soil thus provides data that can be used for "individualizing" soil samples. Although crime labs are not currently using next-generation sequencing, as the technique becomes standard in non-forensic settings, Foran envisions crime labs incorporating it into their work for a host of forensic investigations.

Date Published: September 1, 2017