DNA within cars: prevalence of DNA from driver, passenger and others on steering wheels

Cars are frequently involved in criminal activities and sampled for DNA to assist investigations. To improve our awareness of DNA transfer, persistence, prevalence and recovery (DNA-TPPR) within cars we studied DNA profiles from samples collected from several sites in the front compartment of cars with known histories and occupancies. Here findings relating to steering wheels are reported. Each of the four quarters of the rim as well as the centre column, of four cars, provided good quantities of DNA for profiling. The driver was observed as the sole, major or co-major in 19/20 profiles, and as a minor in the remaining profile generated from these samples. Known close associates, including co-resident partners and passengers/friends, as well as other unknown individuals, who had not driven the car, are also detected on many of the sampled steering wheel sites. More studies are required to improve our awareness of DNA-TPPR and to generate data to help determine probabilities for different profile types and levels of specific contributions given specific circumstances relating to steering wheels, as well as several other relevant areas within cars, to assist sample targeting and activity level assessments.