Investigation of human DNA transfer during mock dog- napping

This study investigated the role of companion animals, specifically dogs, as vectors for human DNA transfer in a simulated crime scene scenario. While human DNA transfer via surfaces and items is well-documented, the potential for pets to serve as DNA reservoirs and subsequent vectors of DNA transfer remains under-investigated. Building upon recent research with cats and dogs, this study examined human DNA transfer dynamics in a mock "dog- napping" scenario. Five dogs were placed into five separate cars, by a recruited handler, which were neither owned by the handler nor familiar to the animals or their owners. The dogs remained in a car for the duration of 20 min and were subsequently returned home for sampling that took place one hour later. The head back and sides were all separately sampled. Each experiment took place on a different day. Various areas of the car (based on the researcher's observations of surface contacts made by a dog) and four sections of the handler's shirt (based on observations of contact between the handler and the dog) were sampled 4-hours and 12-hours post-contact, respectively. DNA was extracted using DNA IQ™, quantified using Quantifiler Trio™ and amplified using Power Plex 21®. The dog owners' DNA was detected most frequently on their respective dogs (85 %) followed by inside of the cars (35 %) and the handler's clothing (10 %). In comparison, the handler's DNA was found on their own shirts (85 %), on the dogs (40 %) and inside the cars (13 %). Notably, the car owners' DNA was detected on the dogs (5 %), on the handler (5 %) (neither of which was directly contacted by the car owners), and inside of the car (47 %). These findings highlight the ease of human DNA transfer during brief contacts and further demonstrate that dogs can effectively serve as vectors of this transfer. The study underscores the vital importance of considering animal-mediated DNA transfer in forensic investigations involving pets, which could influence future evidence collection strategies and interpretations of DNA results in such cases.