A probability-based sampling approach for the analysis of drug seizures composed of multiple containers of either cocaine, heroin, or Cannabis

A probability-based analytical sampling approach for seized containers of cocaine, Cannabis, or heroin, to answer questions of both content weight and identity, is described. It utilizes the Student's t distribution, and, because of the lack of normality in studied populations, the power of the Central Limit Theorem with samples of size 20 to calculate the mean net weights of multiple item drug seizures. Populations studied ranged between 50 and 1200 units. Identity determination is based on chemical testing and sampling using the hypergeometric distribution fit to a program macro – created by the European Network of Forensic Science Institutes (ENFSI) Drugs Working Group. Formal random item selection is effected through use of an Excel®-generated list of random numbers. Included, because of their impact on actual practice, are discussions of admissibility, sufficiency of proof, method validation, and harmony with the guidelines of international standardizing bodies.