Catching an offender from thin air is not that easy: an investigation of air and surface sampling from within cars

Cars are frequently involved in various crimes, making them targets for DNA collection to investigate their usage. This study explores detection of human DNA within cars from the air and various surfaces. The ability to collect human DNA from the air was investigated with the use of the AirPrep™ Cub Sampler ACD220 in seven cars after recent occupation by a pair of temporary users. The resulting air samples were compared to surface samples collected from eight sites within six of these seven cars. The pair of temporary users or ‘intruders’ alternated between roles as a driver wearing new gloves and a facemask, and a front seat passenger who did not wear any personal protective equipment. Results of this study demonstrate that car seats can be valuable DNA sources, though glove and facemask use by an intruder driver can reduce DNA transfer to other contacted areas. Factors such as hours driven, recent cleaning, and shedder status also appear to influence DNA detection on car surfaces. However, air sampling in cars did not produce informative results and future research is necessary to optimize this novel approach.