Crime Scene Investigator Network

Crime Scene Investigator Network Newsletter

This month's newsletter is brought to you by the 2019 CSI Summer Academy

Microbial Communities on Skin
Leave Unique Traces at Crime Scenes

Investigators in two NIJ-supported studies have demonstrated that people carry unique microbial communities on their skin, and traces of those communities, left on touched objects, can be linked to the individual.

When a crime scene is searched for evidence, new research indicates that by swabbing surfaces that were likely touched by a perpetrator, investigators can find an identifiable skin microbial signature the person left behind. Although the work is preliminary and considered a "first step," one of the researchers noted that the work has demonstrated that "skin microbes can ... serve as individual evidence in a variety of scenarios."

Two related NIJ-supported studies evaluated the possibility of using an individual's skin microbiome — a community of micorganisms that inhabit a specific environment — as a form of trace evidence from evidence found at a crime scene. The first study, led by Dr. Rob Knight of the University of California, San Diego, examined whether the sequence in which surfaces are touched by an individual, along with the number of times the surfaces are touched, influences the detection of the person's microbiome.

The study also looked at whether an individual's skin microbial signature is recoverable from an object that had been touched by multiple people, and how long such signatures last on a surface. And finally, the researchers collected samples from deceased individuals at crime scenes and later took samples from the bodies at morgues to determine if the signatures changed after death.

The genetic signatures of these microbes were captured by swabbing and then extracting DNA from the bacteria in each of the samples. The 16s ribonucleic acid (RNA) gene was sequenced so comparisons could be made between bacteria from different samples.

The researchers found that they could distinguish individual microbial signatures, but the results were highly variable based on what type of surfaces were touched (plastic and ceramic surfaces yielded the best results), and how many times they had been touched. Surfaces that had been touched 20 or 30 times gave the best results, and the researchers found that the signatures could persist for at least one day.

The researchers concluded that their data about the "transferability, stability, and individuality of human skin microbiomes" provided "basic information about the conditions under which criminal investigators can match an individual's skin microbial signature to objects or surfaces at crime scenes."

A follow-on study staged two mock residential burglaries to determine if researchers could distinguish the burglars from the residents of the homes. "We sampled the hand and nasal microbiome of 'home occupants' (including cats or dogs) and of the 'invaders', and up to 10 home surfaces," the researchers said. The surfaces included doorknobs, counter tops, and miscellaneous surfaces. After the residents left the home, two researchers, playing the role of burglars, entered and for 30 minutes touched as many random surfaces as they liked. One was wearing nitrile gloves, and the other was not wearing gloves.

Following each 30-minute burglary, another team, wearing shoe covers, facemasks, and hair covers, entered and began swabbing surfaces. Bacteria were gathered, RNA was sequenced, and the researchers tried to distinguish the burglars from the residents.

Analysis showed that some samples could be traced to an individual, "that individual being the possible burglar or entrant to the crime scene," the researchers said. This implies that in the future, extra caution should be taken to protect crime scenes from contamination by police, crime scene personnel, and others, the scientists said.

The researchers concluded that sampling for microbes with the routine swab method is not too onerous and relatively inexpensive, and probably should be conducted at most crime scenes.

About This Article

The research described in this article was funded by NIJ awards 2014-R2-CX-K411 and 2015-DN-BX-K430, with lead researchers from the University of California, San Diego, and the University of Chicago, respectively. This article is based on the grantee reports "Evaluating the Skin Microbiome as Trace Evidence" (pdf 14 pages) by Rob Knight, and "Characterizing Microbial Assemblages as Trace Evidence as Following Residential Burglaries" (pdf 10 pages) by Jack Gilbert.

< read the report "Evaluating the Skin Microbiome as Trace Evidence" >

< read the report "Characterizing Microbial Assemblages as Trace Evidence as Following Residential Burglaries" >

This research is part of a broader portfolio of the forensic application of microbiomes projects managed by NIJ physical scientist Greg Dutton. Find more information on the forensic application of microbiomes or on our trace evidence research portfolio.

National Institute of Justice, "Microbial Communities on Skin Leave Unique Traces at Crime Scenes," December 17, 2018,
This Month's Featured Resource on the Crime Scene Investigator Network Website

The Biological Evidence Preservation Handbook:
Best Practices for Evidence Handlers

Technical Working Group on Biological Evidence Preservation

The Biological Evidence Preservation Handbook offers guidance for individuals involved in the collection, examination, tracking, packaging, storing, and disposition of biological evidence. This may include crime scene technicians, law enforcement officers, healthcare professionals, forensic scientists, forensic laboratory managers, evidence supervisors, property managers, storage facility personnel, lawyers, testifying experts, court staff members, and anyone else who may come in contact with biological evidence. While many of the recommendations relate to the physical storage, preservation, and tracking of evidence at the storage facility, this handbook also covers the transfer of the material between the storage facility and other locations and discusses how the evidence should be handled at these other locations.

This report is divided into five main sections that detail issues and make recommendations related to biological evidence storage, tracking, preservation, and disposition. A glossary, which provides standard definitions of the technical terms used in this report, follows these sections.

<View the Handbook>

New CSI and Forensic Job Announcements

The most comprehensive listing of Crime Scene Investigation and Forensic
employment opportunities on the internet! We typically have over 100 current listings!

To be notified of job openings as they are posted, follow us on Twitter: Job Posting Alerts
or sign up for daily email alerts: Daily Job Posting Alert Emails

Crime Scene Technician
West Melbourne Police Department, West Melbourne, Florida, USA

Final Filing Date: March 8, 2019
Collects, documents, prepares, preserves, and examines physical evidence from crime scenes and persons related to a crime to reconstruct the chain of events for specific crimes. Respond to crime scenes and process physical evidence related to a crime, and possesses general knowledge for latent finger, and/or patent palm or footprint collection using powders or chemicals.
<View complete job listing>
Crime Scene Investigator II
Denver Police Department, Denver, Colorado, USA

Final Filing Date: March 4, 2019
Identify, collect, preserve, and package biological evidence, friction ridge evidence, impression evidence, and other physical evidence according to established standards and existing standard operating procedures; Provides support to crime scene investigations through blood spatter analysis, crime scene reconstruction analysis, ballistic and trajectory analysis and other specialized techniques that require detailed technical knowledge and training;
<View complete job listing>
Criminalist I-IV
Sacramento County District Attorney, Sacramento, California, USA

Final Filing Date: March 13, 2019
Criminalists conduct forensic laboratory analyses of physical evidence, investigate crime scenes, and testify in court as an expert witness on the subjects of forensic analyses and crime scene investigation.
<View complete job listing>

Information Systems & Cyber Security Engineer
City of Rockville Department of Information Technology, Rockville, Maryland, USA

Final Filing Date: March 7, 2019
The Information Systems & Cyber Security Engineer (ISCSE) is responsible for researching, designing, engineering, implementing, supporting and managing security solutions for the City of Rockville.
<View complete job listing>
Property/Evidence Technician
Murrieta Police Department, Murrieta, California, USA

Final Filing Date: March 6, 2019
performs a variety of technical support activities associated with the tracking, handling, control, and safekeeping of evidence and property held by the Police Department; maintains the physical integrity and control of evidentiary items in the City's custody; performs item data input, material cataloging, and processing; ensures the chain of custody of all property and evidence;
<View complete job listing>
Autopsy Technician
Lubbock County Medical Examiner's Office, Lubbock, Texas, USA

Final Filing Date: March 31, 2019
The Autopsy Technician will assist the pathologist in the performance of autopsies, including preparation of the body for autopsy, photography, directly supervised dissections, cleaning and necessary paperwork.
<View complete job listing>

Search for more job listings in Crime Scene Investigations and Forensics
<Crime Scene Investigator Network Employment Listings>

To be notified of job openings as they are posted, follow us on Twitter: Job Posting Alerts
or sign up for daily email alerts: Daily Job Posting Alert Emails

Other Resources on the Crime Scene Investigator Network Website
Not Subscribed to this Newsletter?

If you are not subscribed to this newsletter, you may subscribe with this link: SUBSCRIBE via email
or on our website by clicking here: SUBSCRIBE on our website.

To Unsubscribe

To unsubscribe from future e-mail newsletters, please click here: UNSUBSCRIBE
or email with your request to unsubscribe.

Copyright ©2019 Crime Scene Resources, Inc.

Crime Scene Investigator Network
PO Box 1043
Wildomar, CA 92595-1043