A forensic application of genetic markers for distinction between drug-type and fiber-type Cannabis sativa L.

Genetic markers can represent a valuable tool for forensic purposes in discriminating between fiber-type and drug-type cannabis. The aim of this research was to evaluate developed genetic markers for tetrahydrocannabinolic acid synthase (THCAS) when applied on certified hemp (14 varieties) and forensic casework samples of four chemotypes (40 seizures). Chemotype-associated PCR-based markers did not enable reliable selective amplification despite the difference in cannabinoid composition. In order to characterize forensic samples of unknown origin, THCAS sequencing was performed. The comparison of THCAS sequences, including additional accessions, indicated high genetic similarity of hemp varieties. Confiscated samples of intermediate, THC, CBD and CBG type were clearly separated from fiber-type accessions and assigned to drug-type cluster. Despite the unknown origin, their position on the tree support the notion that they are more related to drug-type accessions than to the fiber-type. However, no clear distinction between chemotypes was found. Furthermore, 26 amino acid substitutions were revealed in THCAS that clearly separate hemp varieties and neither of them cluster with any other tested sample.

Automated summary

Genetic markers are valuable tools in forensic identification of fiber-type and drug-type cannabis. However, chemotype-associated PCR markers are not reliable for forensic samples. THCAS sequencing can characterize samples of unknown origin, showing high genetic similarity among hemp varieties. There is a clear distinction between fiber-type and drug-type cannabis, but no clear distinction among different chemotypes. Amino acid substitutions in THCAS can effectively differentiate hemp varieties.