Presumptive chemical tests

Abstract

Microchemical tests are widely used by forensic scientists as screening tests to assist in the ultimate identification of substances in a wide range of evidence types including drugs, explosive residues, and biological material. Typically, microchemical tests are carried out by mixing a small amount of the test material with a reagent solution to produce a color change or the formation of characteristic microcrystals. These tests are performed either directly on, or after minimal clean-up of, the submitted material. No sophisticated equipment is required for the tests involving color changes as the endpoint of the color test is observed visually, whereas the results of microcrystalline tests will require observation with a microscope. These microchemical tests are only presumptive and any result must be confirmed by an alternative analytical technique, typically chromatography coupled with mass spectrometry. This article provides an overview of presumptive tests, with the exception of those used for serology, and their application to chemical forensic analysis.