Environmental DNA (eDNA) is increasingly being investigated by forensic scientists to use as a new tool that may be used to help solve criminal cases which lack biological traces – and attention is also turning to collecting trace airborne eDNA left behind by intruders in residential burglaries.
An international study, led by Norwegian experts at Oslo University Hospital with collaborators at Flinders University, 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.
The results, 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.
Researchers say 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,” says Flinders Senior Lecturer in Forensic Science Dr Mariya Goray, from the College of Science and Engineering.
This variation in eDNA recovery reflects differences in occupancy patterns, shedding abilities, cleaning and environmental conditions in the burglary simulations, says Flinders University PhD candidate Emily Bibbo, a co-author of the study.
“With further research, these sampling methods could be used in forensic casework in future where crime scenes 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,” says Ms Bibbo.
The study was led by Dr Chiara Fantinato, from the Oslo University Hospital Department of Forensic Sciences, with Flinders University’s Forensic Sciences Lab and the Victorian Police Forensic Services.
Flinders PhD and forensic scientist Dr Duncan Taylor, another coauthor, says 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, adds collaborator Dr Roland van Oorschot, from Victoria Police Forensic Services.
“Standardised sampling, analytical and interpretation procedures and further validation under longer post-event delays and wider environmental conditions would improve collecting reliable results of intruder-associated DNA profiles from residential and other environments,” he says.
