Leveraging genetics to support forensic toxicology analysis: Demonstrating concordance among marijuana samples

Cannabis sativa is an important plant for industrial purposes. Indeed, it is legal to cultivate and supply authorized low level Δ9-tetrahydrocannabinol (THC) cannabis plants for fiber and seeds (i.e., 0.2 % according to the European Union regulation on drugs). Today, chromatography/mass spectrometry-based procedures are successfully applied to determine THC concentration. Unfortunately, when cannabis samples have been degraded because wrongfully stored, toxicological results were affected, altering the final status of legal sample or illegal sample. Rather, genetic identification could give more information about the identity of these plants. For this reason, a degradation study was run to support how genetics can help to detect concordance in cannabis highly-degraded samples. Forty cannabis sub-samples were stored (for one week, two weeks, one month and two months) in auto-sealing bag to assess the effects of a wrong cannabis storage on weight reduction, genomic DNA changes, and corresponding STR profiles. Once respective time-period elapsed, each sub-sample’s weight was measured, the percentage weight loss calculated, and the genomic DNA was extracted and quantified, obtaining a complete STR profile for all samples. Furthermore, the aim of this study was to assess the same 13-loci short tandem repeat (STR) multiplex system used for the degradation experiment and evaluate the power of such markers in the identification and discrimination of highly degraded cannabis samples coming from real cases. The results of this study demonstrated that the 13-loci STR multiplex system successfully achieved the objective both for industry and forensic purposes. For each sample, all 13 loci were amplified, and degraded samples were correctly identified, suggesting that genetic typification could be a useful tool. The proposed procedure could be parallelly applied to toxicology analysis to detect if vegetable sample become from authorized plant, to help courts track back illegal samples or to achieve illegal cannabis genetic profiles for further comparison.