Compendium Developed to Help Forensic Investigators Screen for Drugs

The researchers at the McCrone Research Institute, supported by an NIJ grant, have compiled a compendium of microcrystal tests in order to “fulfill a critical need for reliable analytical methods and assist forensic scientists and other researchers in their work.” The compendium currently contains 19 drugs for which microcrystal tests using various reagents have been previously developed. It describes in detail the microcrystals formed from each test and includes photomicrographs, morphology illustrations, optical properties, notes, and infrared (IR) spectra of the microcrystals.

What Is Microcrystal Testing?

In microcrystal testing, also known as microcrystalline testing, an unknown substance is added to a chemical on a slide. Crystals form that are specific to the substance and can be matched to a known sample through comparison under a microscope.

Microcrystal test techniques can distinguish different types of crystals formed in specific types of chemical reactions and can provide an initial identification for a majority of controlled substances. The scientists who compiled this compendium noted that while some crime labs lack automated drug testing instruments, most have light microscopes and that is all that is needed to do microcrystal testing for illicit drugs. Using only polarized light microscopy, the researchers said that microcrystal tests can identify most illicit drugs specifically and quickly and are inexpensive compared to other methods.

The drugs in this compendium were chosen from the annual reports compiled by the National Forensic Laboratory Information System (NFLIS). Information about known microcrystal tests and from numerous sources spanning past decades were located and evaluated, and a survey of crime laboratories was conducted to determine which reagents and microcrystal tests are currently in use.

The compendium, which includes reagents, microcrystal test methods, optical properties, and IR spectra, will remain a work-in-progress to be updated when new data become available.

About this Article

The work described in the article was performed under NIJ grant number 2011-DN-BX-K528, awarded to the McCrone Research Institute.

This article is based on the grant report Development of A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals, Compendium (pdf, 13 pages") by Gary J. Laughlin.

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