Forensic Science: Finding new ways to catch a thief—via intruders' airborne eDNA

The collection and analysis of biological samples for DNA profiling have become indispensable tools in forensic investigations, facilitating both the incrimination and exoneration of individuals implicated in criminal activities. Every individual constantly release traces of their DNA into their surroundings, depositing genetic material in the environment. Recent advancements in DNA technology have enabled the detection and profiling of these trace samples containing minimal cellular material. These evidences expand the scope of forensic analysis to a new concept of environmental DNA (eDNA) which refers to genetic material recovered from environmental matrices such as water, soil, and air. While eDNA has traditionally been utilized in ecological contexts—such as non-invasive species monitoring and population genetics—its forensic applications are now garnering significant attention. 

Sources of human eDNA

Image source: Springer.com

Environmental DNA (eDNA) is increasingly being investigated by forensic scientists as a tool to help solve criminal cases that lack biological traces—and attention is also turning to collecting trace airborne eDNA left behind by intruders in residential burglaries.

An international study has evaluated the possibility of finding viable evidence from 391 eDNA samples collected from air, dust and surfaces in simulated 15-minute residential burglaries in 22 households in Oslo and Australia. (1)

The study, published in Forensic Science International: Genetics, used novel techniques to find evidence of human intruder eDNA from air samples collected under controlled conditions—with varying degrees of success depending on air temperatures, humidity, dust, existing household DNA and other factors.
Analysis of 391 air, dust and surface samples from simulated 15-minute burglaries in 22 homes demonstrated recovery of intruder-associated DNA, with variable success. Airborne DNA may complement dust and surface evidence, but forensic use requires further validation and standardized methods to account for background DNA, contamination and environmental conditions.

Researchers say that the brief nature of such crimes, combined with offenders' efforts to avoid detection and the difficulty of targeting the exact locations where DNA traces were deposited, may result in limited or absent biological evidence.

Human eDNA can accumulate at a crime scene through passive shedding and dispersal throughout the environment, including in airborne particles and dust, where it may persist despite cleaning efforts.
This variation in eDNA recovery reflects differences in occupancy patterns, shedding abilities, cleaning and environmental conditions in the burglary simulations.
With further research, these sampling methods could be used in forensic casework in the future where crime scene procedures include careful interpretation of contamination risk, the presence of resident and unknown background DNA, and other environmental influences which could affect airborne DNA recovery, say the experts.

The rapid entry and exit by experienced burglars wearing gloves and protective clothing means DNA traces may be absent, present in low quantities, degraded or consist of complex mixtures, thereby reducing the potential for biological evidence to support investigations.

However, the study found that when combined with eDNA from dust and surfaces, airborne DNA may contribute to reconstruction of recent and established occupancy patterns.
Standardized sampling, analytical and interpretation procedures and further validation under longer post-event delays and wider environmental conditions would improve the collection of reliable results of intruder-associated DNA profiles from residential and other environments.

Results from the tests at four locations provide a proof-of-concept foundation for further research into the forensic use of human airborne eDNA from household crime scenes.

Footnotes:

1. Chiara Fantinato et al., Human airborne eDNA as forensic evidence in simulated residential burglaries, Forensic Science International: Genetics (2027). DOI: 10.1016/j.fsigen.2026.103618