Covert and improvised sampling of DNA using unconventional sampling tools for deployed operatives

Utkarsh Keswani

Advancements in the science and technology of DNA analysis in forensic science led to greatly reduced amounts of starting DNA required for testing. This reduction allowed for research into more trace forms of DNA such as touch DNA. Touch DNA is defined as cellular deposits left on a surface after direct physical contact. This can prove to be beneficial in covert surveillance and evidence collection since it can allow an operative to collect a person of interest’s (POI) genetic information for intelligence purposes. There are several challenges with the deposition of touch DNA onto a surface. External factors such as surface type, time between deposition and collection, persistence of touch DNA, surface contaminants as well as force and duration of impact all affect the amount of cellular material deposited. Additionally, intrinsic factors such as age and skin diseases of the donor affect deposition as well. Thus, unless a large number of volunteers and replicates are used, touch DNA is not a reliable DNA source to test the recovery efficiency of a sampling method since the amount of DNA deposited is unknown as well as highly variable across replicates. A meta-analysis of 40 research publications showed that 29 out of the 40 articles exclusively used touch DNA as a DNA source. There needs to be further discourse around the use of touch DNA in forensic research and better alternatives need to be considered for studies lacking large sample numbers with multiple replicates. A possible solution is the use of analogous quantifiable cell types such as buccal or epithelial cells to evaluate a sampling or collection method. This review also focused on covert and improvised sampling and the use of by-chance evidence by law enforcement. By-chance evidence can be defined as the collection of any material discarded by a POI in public which can be used as evidence or intelligence. In a DNA context, there a few challenges with by-chance evidence. Since these items can only legally be collected in public, there is increased risk of contamination. It is also possible that the wrong item is collected or that the POI may not discard anything of evidentiary value in public. This shows the need for a solution that can improve targeted sampling of a POI while ideally not requiring the operative to possess any specialized training or equipment for DNA sampling. These challenges can be addressed by eliminating the collection of a discarded item and instead focusing on sampling touch DNA left behind by a POI.

Covert and improvised sampling of DNA using unconventional sampling tools for deployed operatives

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