Representative Sampling of Drug Seizures in Multiple Containers

Abstract

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.

Optimization of Evidence Analysis Cost Using Arbitrary Re-Sampling Techniques for Sample Influx into Forensic Science Laboratory

“…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 [14]. However, such resampling must have scientific basis.…”

“…Forensic scientist shall evaluate which items to analyze in a case based on several factors, which include nature of potential charge(s), location of item, and the nature of the item, i.e., biohazards, chemical hazards and insufficient sample [5] [14]. The sample influx from the investigation teams determines the population or multiple unit items (MUI) to sample from.…”

The application of portable microchip electrophoresis for the screening and comparative analysis of synthetic cathinone seizures

“…Alternative methods based on frequentist or Bayesian statistical approaches Page 3 of 20 A c c e p t e d M a n u s c r i p t are also employed. The frequentist approach makes use of a hypergeometric sampling population table, whilst the Bayesian model makes use of prior knowledge and applies Baye's theorem to select a suitable sample size for analysis [8][9][10]. In comparison to classical methods, the frequentist and Bayesian methods are more cost-effective and timely and still provide adequate information for the purposes of law enforcement and judicial inquiry.…”

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

“…Variations of the sampling approach and related issues in the context of seized-drug analysis have been described in journal articles and texts [1][2][3][4][5][6][7][8][9][10][11][12]. International standardizing bodies have published helpful terminologies and protocols on the subjects of sampling and statistics in general [13,14] and on seized-drug sampling in particular [14].…”