Effect of UV exposure on DNA deposited on drug capsules

Abstract

Illicit drugs are often made in less-than-sterile environments and can be stored in ways which can be detrimental to any DNA present, such as whether they are exposed to UV radiation. Previously, analysis of how exposure to UV impacted DNA for forensic applications has been in controlled laboratory conditions isolating a single component of UV radiation and often on DNA-rich samples such as bloodstains or saliva. To evaluate DNA persistence in more realistic conditions, capsules, such as those used to distribute controlled substances, were manually made and then packed into ziplock bags. The persistence of DNA deposited on capsules was examined when left indoors in either, complete darkness, direct sunlight in high UV conditions (summer) or in low UV conditions (winter) for three weeks in ambient room temperature. The DNA yield, STR DNA profile quality and degradation index were all analysed to determine the impact of varied UV exposure on DNA in a semi-temperature-controlled environment. Capsule samples exposed to high UV conditions had significantly reduced DNA yields, a lower number of alleles from the capsule handler and, thus, reduced likelihood ratios compared to capsules exposed to darkness and low UV conditions. Samples exposed to either darkness or low UV had little-to-no differences in all DNA quality measures tested. Despite a decreased DNA yield and poorer quality DNA profiles, capsules left in high UV conditions for three weeks have sufficient DNA for DNA profiles with over half the genetic information present. The storage conditions of drug capsules, either before or after seizure by law enforcement, can impact the DNA persistence in as little as three weeks, which is problematic for often already low concentrations of DNA in trace samples.