Forensic serology

Forensic serology is the detection, classification and study of various bodily fluids such as blood, semen, fecal matter and perspiration, and their relationship to a crime scene. A forensic serologist may also be involved in DNA analysis and bloodstain pattern analysis.

A combination of two tests are generally performed. One is a catalytic test such as Hemastix or the Kastle-Meyer test, which is based on the peroxidase-like activity of hemoglobin. The other is the Takayama Crystal Assay, which forms a ferro protoporphyrin ring by a reaction between pyridine and the iron atom of the heme group. Testing for traces of blood using the Luminol process is also used by scene of crime investigators.

Semen identification is usually accomplished by combining a UV test, an acid phosphatase test, and a microscopic slide search for spermatozoa. If no spermatozoa are seen on the prepared slide, a test for the presence of P30 (also known as prostate specific antigen) is commonly performed.

Common saliva detection techniques are based on the activity of the enzyme alpha-amylase which breaks down starches from food into smaller oligosaccharide molecules, starting digestion in the mouth. In testing, the alpha-amylase breaks down starches present and creates a color change.

A starch iodine gel contains agarose and starch. Samples are added to the gel and allowed to diffuse through the gel overnight. Visualization is accomplished by adding iodine to the gel which stains the starch in the gel blue. When saliva is present, the alpha-amylase breaks down the starches, creating a clear circle around the sample well.

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