Detecting personal microbiota signatures at artificial crime scenes

Area of Science:

• Microbiology
• Forensic Science
• Human Microbiome

Background:

• Humans continuously shed millions of microbial cells, creating a potential forensic trace.
• The unique microbial signatures on human skin offer a possibility for identifying individuals in forensic investigations.

Purpose of the Study:

• To investigate the potential of using 16S rRNA amplicon sequencing to identify human microbial signatures on surfaces for forensic applications.
• To assess the accuracy and reliability of microbial profiling in mock burglary scenarios and track microbial persistence over time.

Main Methods:

• 16S rRNA amplicon sequencing was used to analyze microbial communities on skin and building surfaces.
• Experiments included controlled interactions, uncontrolled incidental contact with a door handle, and mock burglaries in ten residences.
• Microbial profiles were compared against a population of 600 individuals to assess uniqueness and traceability.

Main Results:

• Individuals leave unique microbial signatures (unique exact sequence variants - uESVs) on surfaces, with 60-77% originating from hands.
• The accuracy of identifying a specific burglar in mock crime scenes was low, ranging from 20-25%.
• Microbial signatures on door handles did not significantly decay over time, regardless of human presence.

Conclusions:

• While human microbial signatures are detectable and unique, current 16S rRNA amplicon sequencing methods are not yet reliable enough for forensic trace evidence standards.
• Further research is needed to improve the accuracy and reliability of microbial forensics for criminal investigations.