An international research team led by Norwegian experts at Oslo University Hospital has shown that future forensic crime scene investigators could soon collect DNA left behind by home invaders from thin air.
The research team said environmental conditions affected the quality of the results. However, their simulated home invasions still showed successful forensic collection of airborne DNA evidence, even if the would-be thief cleaned up afterward.
Although law enforcement does not yet have the technology, the team said improvements already underway could help investigators rebuild a crime scene when more traditional evidence is corrupted or missing.
Pulling DNA Out of Thin Air Could Even Catch Careful Home Invaders
According to a statement announcing the research, forensic scientists are already exploring trace DNA left behind at crime scenes where cases “lack biological traces.” Called environmental DNA (eDNA), these tiny pieces of biological material can stick to dust or other surfaces long enough for crime scene investigators to collect them for laboratory analysis.
In the new study, the team explored the possibility of collecting DNA evidence left behind by intruders from thin air. The researchers said such evidence could be vital when investigating home invasion crimes since they are typically very brief by nature.
Study co-author and Flinders PhD and forensic scientist Dr Duncan Taylor explained that traditional DNA evidence may be absent, present in low quantities, degraded, or become mixed with other organic or biological materials. The problem can be compounded by a home invader’s efforts to conceal themselves, including wearing gloves or other protective clothing or cleaning up.
However, according to Flinders Senior Lecturer in Forensic Science, Dr Mariya Goray, human eDNA can accumulate at a crime scene through passive shedding and dispersal throughout the environment. This includes leaving behind DNA traces in airborne particles and dust, “where it may persist despite cleaning efforts.”
Tool Can Help Forensic Investigators Reconstruct a Crime Scene
To test the concept, study leader Dr. Chiara Fantinato, from the Oslo University Hospital Department of Forensic Sciences, performed a series of “simulated” residential home invasions and burglaries. To attain the best possible real-world results, including the existence of eDNA from actual residents, each 15-minute mock home invasion was conducted at 22 real households in Oslo and Australia.
Working with scientists from Flinders University’s Forensic Sciences Lab and the Victorian Police Forensic Services, the team analyzed the airborne samples looking for evidence of the volunteer home invaders. According to the team, these initial experiments achieved “varying degrees of success” in identifying the home invader.
“The study found that when combined with eDNA from dust and surfaces, airborne DNA may contribute to reconstruction of recent and established occupancy patterns,” they explained.
The largest variances in the results were attributed to differences in air temperature, humidity, dust, existing DNA already in the household, and “other factors.” Study co-author and Flinders University PhD candidate Emily Bibbo said the variances reflected differences in occupancy patterns, “shedding abilities,” and environmental conditions in the burglary simulations.
The team also evaluated the differences when the simulated home invader tried to clean up afterward. According to the team, cleanup efforts affected the results, but not enough to completely hide the simulated criminal’s identity.
More Reliable Results of “Intruder-Associated” Genetic Profiles
When discussing the study’s results, the authors said that their efforts to collect home invader eDNA out of thin air provided a successful proof-of-concept foundation for “further research into the forensic use of human airborne eDNA from household crime scenes.”
Ms. Bibbo said further research could make eDNA airborne collection a critical tool for forensic scientists where crime scene procedures include the “careful interpretation of contamination risk, the presence of resident and unknown background DNA, and other environmental influences which could affect airborne DNA recovery.”
Dr Roland van Oorschot from Victoria Police Forensic Services said future improvements to eDNA collection from thin air should include standardized sampling methods and established analytical and interpretation procedures. Dr. van Oorschot said researchers should continue to explore “further validation under longer post-event delays and wider environmental conditions.”
“[These steps] would improve collecting reliable results of intruder-associated DNA profiles from residential and other environments,” the researcher explained.
The study’s findings were published in Forensic Science International: Genetics.
Christopher Plain has spent the last six years as Associate News Editor and Head Science Reporter at The Debrief. Follow and connect with him on X, learn about his novels at plainfiction.com, or email him at christopher@thedebrief.org.