Traditional trace DNA recovery often relies on contact traces or body fluids, which may be limited or absent, particularly in cases involving brief occupancy. We have previously demonstrated that human environmental DNA (eDNA) can be used to detect recent and past occupants of indoor premises, highlighting its potential as a novel source of forensic evidence. Here, we evaluated human eDNA recovery in simulated residential burglaries and assessed its potential use to detect intruders. A total of 391 samples were collected from air, dust, and surfaces in 22 households by two laboratories. Samples were recovered under two conditions: immediately after regular occupants vacated and following a 15-minute simulated burglary. Air samples were collected using the AirPrep ACD220 sampler, while dust and surface samples were recovered using moistened cotton swabs from dusty undisturbed areas and surfaces contacted during the intrusion. Resulting DNA profiles were compared against reference databases containing profiles of residents and intruders. The findings demonstrate the unique potential of airborne DNA evidence. Air sampling under normal occupancy conditions enabled detection of regular occupants, whereas airborne DNA collected 30 minutes after the simulated burglaries identified intruders in 82% of cases in one laboratory and 36% in the other. When integrated with dust and surface samples, airborne DNA provided complementary evidence for detecting legitimate household occupants including relatives and past visitors. Variation in eDNA recovery across households and laboratories was observed, likely reflecting differences in occupancy patterns, environmental shedding abilities, cleaning routines, environmental conditions, and laboratory-related factors. This is the first study that demonstrates the potential of using airborne DNA to detect individuals soon after exiting, following as little as 15 minutes of occupancy. The results support the further development of human eDNA as a complementary source of evidence, particularly in brief crimes where conventional traces may be scarce.

Authors

• Ane Elida Fonneløp (Department of Forensic Sciences, Oslo University Hospital; Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Norway)
• Chiara Fantinato (Department of Forensic Sciences, Oslo University Hospital, Norway)
• Emily Bibbo (College of Science and Engineering, Flinders University, Australia)
• Peter Gill (Department of Forensic Sciences, Oslo University Hospital, Norway)
• Roland van Oorschot (Office of Chief Forensic Scientist, Victoria Police Forensic Services Department;  School of Agriculture, Biomedicine and Environment, La Trobe University, Australia)
• Duncan Taylor (College of Science and Engineering, Flinders University; Forensic Science SA, Australia)
• Mariya Goray (College of Science and Engineering, Flinders University, Australia)