Statistical and legal aspects of the forensic study of illicit drugs

Prosecuting those arrested for the unlawful possession, distribution or importation of illicit drugs, such as powder cocaine, crack cocaine, heroin and LSD, is usually both time-consuming and expensive, primarily because of the need to determine "beyond a reasonable doubt" the total amount of drugs seized in each case. Accuracy is important since penalties (imprisonment or fines) depend upon the quantity seized. Substantial backlogs in processing drug cases often develop as a result. In some jurisdictions, complete testing and analysis of all substances seized from a defendant are customary in support of a case, while in other jurisdictions random sampling of drugs and the subsequent presentation of an estimate of the total amount seized have been used for many years. Due to pressure from crime laboratories and prosecutors, who point to major increases in their caseloads as well as a trend toward decreasing funding and staffing for the crime laboratories, jurisdictions which currently carry out a complete census of all seized evidence are now seriously considering a change in their methodology with a view to instituting new guidelines for the scientific sampling of evidence. In this article, we discuss the statistical and legal issues that have arisen in cases involving illicit drugs.