Forensic Science International
Volume 197, Issue 1 , Pages 105-113, 15 April 2010

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

  • John R. Mario

      Affiliations

    • Corresponding Author InformationTel.: +1 631 853 5585; fax: +1 631 853 5739.

Suffolk County Crime Laboratory Drug Chemistry Section, Office of the Chief Medical Examiner, Hauppauge 11788, NY, USA

Received 11 June 2009; received in revised form 22 December 2009; accepted 4 January 2010. published online 08 February 2010.

Abstract 

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.

Keywords: Seized-drug analysis, Sampling, ENFSI, SWGDRUG, ASTM

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PII: S0379-0738(10)00007-1

doi:10.1016/j.forsciint.2010.01.001

Forensic Science International
Volume 197, Issue 1 , Pages 105-113, 15 April 2010

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