A study of DNA transfers onto plastic packets placed in personal bags

Illicit drug distribution: Evaluation of DNA transfer between ziplock bags and capsules

Powders containing illicit substances are frequently poured into capsules and then distributed in small bags to users, often via intermediaries. We report on the transfer of DNA between individuals involved in making, packing, and transporting capsules within ziplock bags (ZLB) via two pathways, each using 10 ZLBs. A two-person chain was created where participant A made and packed the capsules into ZLBs and participant C then carried the bags for four days. A three-person chain was devised where participant A made the capsules, participant B placed the capsules in bags, and participant C carried the bags. The ZLBs were sampled for DNA on the inside, the inner semi-protected portion of the opening, and the outside surface. The exterior of capsules were also sampled along with a storage container. DNA profiling using Verifiler™ Plus was performed with data deconvoluted by STRmix™. Informative DNA profiles were obtained from capsules despite evidence of DNA transfer from the capsules to both storage containers and the inside of the ZLB. The outside of ZLBs yielded complex mixtures, however, the inside of the bag and the exterior of capsules, which had greater protection, yielded profiles with predominately only one to two contributors. This highlights that the inside of the bags and exterior of capsules could be targeted to identify individuals involved in the early packaging stages of the illicit drug pathway while the outside provided more information on recent handling.

Trace DNA and its persistence on various surfaces: A long term study investigating the influence of surface type and environmental conditions - Part two, non-metals

The work presented herein is the second part of a large-scale persistence project aimed at identifying trends in trace DNA persistence. This study aims to show how different environmental storage conditions and target surface characteristics influence the persistence of cellular and cell free DNA (cfDNA) over time. To eliminate variation within the experiment, we used a proxy DNA deposit consisting of a synthetic fingerprint solution, cellular DNA, and/or cfDNA. Samples were collected and analysed from eight non-metal surfaces over the course of 1 year (27 time points) under three different environmental storage conditions. The results of this experiment show that surface characteristics in conjunction with DNA type greatly influence DNA persistence. Variation in the amount of DNA recovered over time was greatly influenced by surface porosity. CfDNA persisted at significantly higher levels on non-porous surfaces, and cellular DNA persisted at higher levels on porous items. Furthermore, statistically significant differences in DNA persistence were found among the items classified as non-porous surfaces and among the items classified as porous surfaces. Additionally, this study showed that the sample storage environment had a larger impact on DNA persistence than previously observed for metal surfaces [1]. When considering DNA type, cellular DNA was shown to persist for longer than cfDNA and persistence as a whole appears to be better when DNA is deposited alone rather than in mixtures. Unsurprisingly, it was found that the amount of DNA recovered from trace deposits decreased over time. However, DNA decay is highly dependent on the surface type and exhibits higher variability at short time points and on porous surfaces. For each of the surfaces tested, DNA persisted 1 year past deposition (in some combination of DNA type and environmental condition), except for wood, on which DNA did not persist in any capacity past four months. This data is intended to add to our understanding of DNA persistence and the factors which affect it.