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Developing Reliable Methods for Microbial Fingerprinting of Soils

NCJ Number
Date Published
March 2015
105 pages
Since there is currently no reliable and objective method for individualizing soil, this research project examined the utility of soil bacterial profiling via next-generation sequencing of the 16S rRNA gene, so as to identify a soil's origin.

This is an important forensic issue because soil evidence has the potential of being a valuable tool for linking a suspect, victim, or item to a crime scene. Currently, however, only class characteristics of soil are considered in traditional analysis. Using the methods described in this report, diverse and similar habitats were successfully differentiated in both multidimensional space and through supervised classification, which accurately classified soil samples back to their locations of origin 100 percent and 87.5 percent of the time, respectively. Time and space within a habitat did not affect bacterial profiles enough to hinder location-of-origin assignment, where samples were correctly classified an average of 96 percent of the time. Soil collected from evidentiary items exhibited abundance change of certain taxonomic classes, but remained clustered nearest its location of origin with 100-percent accuracy, even after a full year or long-term storage. Thus, the success in tracing soils back to a location of origin demonstrates the potential of next-generation sequencing of bacteria, in conjunction with a combination of robust statistical techniques, for the individualization of forensic soil samples. The methodology is detailed. 34 figures, 4 tables, and 43 references

Date Published: March 1, 2015