A new study, published in Forensic Science International: Genetics, has shown for the first time that DNA can be obtained from the exterior of drug capsules. This discovery offers a new method for tracking down individuals involved in the illegal drug trade.
The illegal drug trade is a global problem with known detrimental impacts on society. A common illicit drug is MDMA, also known as ecstasy.
In Australia, where this study was based, ecstasy is increasingly being found as loose crystals packaged in capsules rather than tablets. Capsules enable the drug to be distributed in a purer form, as extra ingredients are not required to maintain structural integrity.
The increasing use of capsules is making the collection of chemical fingerprints trickier. Chemical fingerprints establish the synthetic pathway used to produce the drugs. A consequence of the lack of additives in capsules is that there are fewer chemical compounds available for profiling. New approaches to examine drug preparations are therefore required to provide more forensic detail on seized drugs.
Trace DNA is incredibly important evidence in forensic investigations. Powdered drugs have to be manually loaded into capsules, providing many opportunities for DNA deposition to occur. However, DNA deposited through touch is generally of lower quantity and quality than DNA from saliva. In addition, individuals can have non-self DNA present on their hands, producing a mixed profile. These features present difficulties in analysing touch-deposited DNA.
Due to these challenges, no study has yet tested the exterior of capsules for DNA despite their extensive manual handling. In fact, drugs themselves are not routinely sampled in forensic investigations. As short tandem repeat (STR) profiling technology has greatly improved in recent years, the researchers of this study sought to discover if it is possible to recover traces of DNA deposited by touch.
Profiles from drug capsule exteriors
The researchers aimed to generate informative human STR profiles from capsule exteriors. Such profiles would have the potential to identify individuals involved in drug production and distribution. In total, 60 capsules that had been touched for 15 seconds each by an individual were tested for DNA samples.
The average amount of DNA recovered from the capsules was 0.267 ng. The generation of profiles was possible from 82% of capsules, with full profiles obtained for 25% of the samples. Overall, 80% of the profiles had sufficient enough DNA to be classed as informative. Although non-self DNA was transferred, the majority of DNA recovered was that of the individuals. In forensic investigations, these STR profiles could be matched to profiles on DNA databases of known individuals. However, if no match is found, the profiles can still provide valuable information.
Professor Adrian Linacre, chair in Forensic DNA Technology at Flinders University, said: “If an unidentifiable DNA profile is obtained, it may still be useful for intelligence-led policing as a ‘biological profile’ to potentially link or exclude various drug seizures as originating from the same source to complement and corroborate the findings of the chemical profile.”
This study was preliminary, so further work will need to be carried out to validate these findings. However, the results gathered confirm that even after only 15 seconds of handling, capsule exteriors retain enough DNA to produce informative profiles. In the future, biological profiling could be used alongside chemical profiling in investigations of illegal drug distribution.
Amy Griffin, PhD candidate and co-author, said:
“The ability to generate profiles from 82% of capsules highlights how valuable it could be for operational forensic laboratories to sample the exterior of pill capsules.”
“Our methodology is compatible with systems already implemented in DNA laboratories, which easily facilitates the examination of illicit drug capsules for DNA. With the baseline of DNA transfer established, further research is underway by us to investigate this application when capsules are handled in a more realistic scenario encountered in police work.”