REPRESENTATIVE SAMPLING OF DRUG SEIZURES IN MULTIPLE CONTAINERS

Exhibits of illicit drugs in a large number of containers are frequently submitted to crime laboratories. The forensic chemist often needs to select randomly and then examine a number of these containers to provide information regarding the composition of the overall exhibit which is sufficient to support the requirements of the criminal justice system. Although various methods of sampling can be shown to provide samples that will allow statistical inferences to be made with a high degree of confidence, no procedure has been identified that specifically meets the sampling objectives associated with an exhibit of this sort. The authors have addressed this sampling problem by applying the probability theory of the hypergeometric distribution to the sampling of drug exhibits contained in multiple containers. The resulting model will permit strong probability statements to be made regarding the presence of the controlled substance in a predetermined quantity of the exhibit, thereby supporting the prosecution and sentencing of violators of controlled substance laws.