Genetic testing services now sequence a leaf sample and compare it against a database, which gives a way to check whether a pack labelled as a famous cut is related to it. The results do not say anything about THC directly, but they expose renamed or mislabelled lines quickly. Several breeders whose THC seeds are stocked on https://potentthcseeds.com publish their sequencing results, which is a level of openness the industry did not have five years ago. Expect this to become the norm for anything sold at a premium.