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Forensic Science Communications

January 2005 – Volume 7 – Number 1

Standards and Guidelines

Methods of Analysis/Drug Identification

Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG)

October 2003

Introduction | Categorizing Analytical Techniques | Identification Criteria | Comment

1. Introduction

The purpose of Methods of Analysis/Drug Identifification is to recommend minimum standards for the forensic identification of commonly seized drugs. It is recognized that the correct identification of a drug or chemical depends on the use of an analytical scheme based on validated methods and the competence of the analyst. The Scientific Working Group for the Analysis of Seized Drugs requires the use of multiple uncorrelated techniques. It does not discourage the use of any particular method within an analytical scheme, and it is accepted that unique requirements in different jurisdictions may dictate the actual practices followed by a particular laboratory.

2. Categorizing Analytical Techniques

Techniques for the analysis of drug samples may be classified into three categories based on their discriminating power. Table 1 provides examples of these techniques listed in order of decreasing discriminating power from A to C.

**Table 1: Categories of Analytical Techniques**
Category A	Category B	Category C

Infrared spectroscopy	capillary electrophoresis	color tests
mass spectrometry	gas chromatography	fluorescence spectroscopy
nuclear magnetic resonance spectroscopy	ion mobility spectrometry	immunoassay
Raman spectroscopy	liquid chromatography	melting point
	microcrystalline tests	ultraviolet spectroscopy
	pharmaceutical identifiers
	thin layer chromatography
	cannabis only: macroscopic examination microscopic examination

3. Identification Criteria

The Scientific Working Group for the Analysis of Seized Drugs recommends that laboratories adhere to the following minimum standards:

3.1.	When a validated Category A technique is incorporated into an analytical scheme, then at least one other technique (from either Category A, B, or C) must be used.
	3.1.1.	This combination must identify the specific drug present and must preclude a false-positive identification.
	3.1.2.	When sample size allows, the second technique should be applied on a separate sampling for quality assurance reasons. When sample size is limited, additional measures should be taken to assure that the results correspond to the correct sample.
	3.1.3.	All Category A techniques must have reviewable data.
3.2.	When a Category A technique is not used, then at least three different validated methods must be employed.
	3.2.1.	These in combination must demonstrate the identity of the specific drug present and must preclude a false-positive identification.
	3.2.2.	Two of the three methods must be based on uncorrelated techniques from Category B.
	3.2.3.	A minimum of two separate samplings should be used in these three tests. When sample size is limited, additional measures should be taken to assure that the results correspond to the correct sample.
	3.2.4.	All Category B techniques must have reviewable data.
3.3.	For the use of any method to be considered of value, test results must be considered positive. Although negative-test results provide useful information for ruling out the presence of a particular drug or drug class, these results have no value toward establishing the forensic identification of a drug.
3.4.	In cases where hyphenated techniques are used (e.g., gas chromatography-mass spectrometry, liquid chromatography-diode array ultraviolet spectroscopy), they will be considered as separate techniques if the results from each are used.
3.5.	Cannabis exhibits tend to have characteristics that are visually recognizable. Macroscopic and microscopic examinations of cannabis will be considered, exceptionally, as uncorrelated techniques from Category B when observations include documented details of botanical features. Additional testing must follow the scheme outlined in Sections 3.1 or 3.2. For exhibits of cannabis that lack sufficient observable macroscopic and microscopic botanical detail (e.g., extracts or residues), D9-tetrahydrocannabinol (THC), or other cannabinoids must be identified using the principles set forth in Sections 3.1 and 3.2.
3.6.	Examples of reviewable data are as follows:
	3.6.1.	Printed spectra, chromatograms, and photographs or photocopies of thin layer chromatography plates.
	3.6.2.	Contemporaneous, documented peer review for microcrystalline tests.
	3.6.3.	Recording of detailed descriptions of morphological characteristics for cannabis (only).
	3.6.4.	Reference to published data for pharmaceutical identifiers.

4. Comment

These recommendations are minimum standards for the forensic identification of commonly seized drugs. However, it should be recognized that they may not be sufficient for the identification of all drugs in all circumstances. Within these recommendations, it is up to the laboratory's management to determine which combination of analytical techniques best satisfies the requirements of its jurisdiction.