Forensic Drug Analysis The challenge or difficulty of forensic drug identification comes in selecting analytical procedures that will ensure a specific identification of a drug. This plan, or scheme of analysis, is divided into two phases. A preliminary analysis that is nonspecific and preliminary in nature to reduce the possibilities to a manageable number. A confirmation determination that is a single test that specifically identifies a substance.

Forensic Drug Analysis Screening, Confirmation, and Color Tests Analysts use screening tests to determine the identity of drugs present in a sample. A screening test is a preliminary test used to reduce the possible identities of unknown substances to a small and manageable number.

Forensic Drug Analysis Screening, Confirmation, and Color Tests A series of color tests produce characteristic colors for the more commonly encountered illicit drugs.

Forensic Drug Analysis Screening, Confirmation, and Color Tests In a microcrystalline test, a drop of a chemical reagent added to a small quantity of a drug on a microscope slide produces crystals highly characteristic of a drug.

Forensic Drug Analysis The Specific Tests After preliminary testing, forensic chemists use more specific tests to identify a drug substance to the exclusion of all other known chemical substances. Chromatography is a means of separating and tentatively identifying the components of a mixture.

Forensic Drug Analysis The Specific Tests Thin line chromatography (TLC) uses a solid, stationary phase, usually coated onto a glass plate, and a mobile liquid phase to separate the components of the mixture.

Forensic Drug Analysis The Specific Tests Gas chromatography (GC) separates mixtures on the basis of their distribution between a stationary liquid phase and a mobile gas phase.

Forensic Drug Analysis The Specific Tests Spectrophotometry is the study of the absorption of light by chemical substances.

Forensic Drug Analysis The Specific Tests More forensic laboratories use ultraviolet (UV) and infrared (IR) spectrophotometers to characterize chemical compounds.

Forensic Drug Analysis The Specific Tests IR spectrophotometry provides a far more complex pattern than UV spectrophotometry. Because different materials have distinctively different infrared spectra, each IR spectrum is equivalent to a “fingerprint” of that substance.

Forensic Drug Analysis The Specific Tests Mass spectrometry characterizes organic molecules by observing their fragmentation pattern after their collision with a beam of high-energy electrons

Forensic Drug Analysis The Specific Tests Infrared spectrophotometry and mass spectrophotometry typically are used to specifically identify a drug substance.

Collection and Preservation of Drug Evidence The field investigator has the responsibility of ensuring that the evidence is properly packaged and labeled for the laboratory. Generally common sense is the best guide, keeping in mind that the package must prevent the loss of the contents and/or cross-contamination. Often the original container in which the drug was seized will suffice. All packages must be marked with information that is sufficient to ensure identification by the officer in the future and establish the chain of custody.