The Minnesota Bureau of Criminal Apprehension (BCA) uses many different procedures to identify various bodily fluids. The identification of bodily fluids is known as serology. Currently, BCA serology includes blood, semen, saliva, and urine identification.
The phenolphthalein test is used to presumptively test for the presence of blood. The chemicals used are ethanol, phenolphthalein, and hydrogen peroxide. Phenolphthalein testing works through a Redox reaction where the chemicals start in a reduced form. If peroxidase activity from the heme group (found on the Hemoglobin molecule in blood) is present, the chemicals are oxidized. If oxidation occurs, a color change (to bright pink) is observed. If there is no peroxidase activity, then the oxidation will not occur and no color change will be observed.
Pink color change = presumptively positive for blood*
No color change = negative for blood
The HemaTrace™ test is used to determine if a bloodstain is of human origin. This test is an antigen-antibody reaction. The antibodies are present on the HemaTrace™ card and if the antigen (the heme group of the Hemoglobin molecule) is present, then an antibody-antigen reaction occurs on the test site (T) of the card. The antigens and antibodies bind to each other and form a lattice (chain) which causes a pink dye band to be visible. The control region of the test strip should always have a reaction, and the pink dye band should be visible on both positive and negative results.
Pink line in control region + pink line in test region = presumptively positive result for human blood*.
Pink line in control region only = negative result for human blood.
*Note: both phenolphthalein and Hematrace™ are presumptive tests. Further DNA testing can confirm these results.
Potential semen stains can be identified using ALS (alternative light source). Semen stains will fluoresce, along with other body fluids and various other stains. These fluorescent stains can then be swabbed and tested using BCIP (5-Bromo-4-chloro-3-indolyl phosphate). BCIP reacts with the acid phosphatase found in seminal fluid. When acid phosphatase is present, the reaction will cause the swabs to turn teal blue. BCIP testing is typically done on items of clothing or bedding. The BCIP test is a presumptive test for the presence of semen &/or seminal fluid.
p30 is a presumptive test for the presence of human prostate-specific p30 protein found in seminal fluid. The p30 test works through an antigen-antibody reaction. Antibodies are present on the p30 card and if the antigen is present (p30 protein) in a sample, then a reaction occurs on the test site (T) of the card. The antigens and antibodies bind to each other and form a lattice (chain) which causes a pink dye band to be visible. The control region of the test strip should always have a reaction, and the pink dye band should be visible on both positive and negative results. The p30 test is a presumptive test for the presence of semen &/or seminal fluid.
Pink line in control region + pink line in test region = positive result for p30 protein/seminal fluid.
Pink line in control region only = negative result for p30 protein/seminal fluid.
Sperm Hyliter is a slide staining technique used to microscopically identify sperm. Sperm Hyliter™ also works through an antigen-antibody reaction. During the staining process, the sperm heads react with an antibody found in the stain. This reaction causes the sperm heads to fluoresce a bright green color. A second stain is added that stains all of the nuclei in a sample. Therefore, when sperm are present in a sample they will fluoresce green or blue when viewed under two different contrasts (FITC & DAPI) on the microscope.
This fluorescence makes the sperm heads easy to distinguish from the surrounding cells/debris. This reaction is specific to human sperm heads. When identifying sperm heads one looks for the correct fluorescence along with the right size, shape, and the presence of an acrosome; which is a small unstained part of the sperm head. Positive identification of sperm microscopically is the only confirmatory test for semen identification used at the BCA.
Christmas Tree Stain
Christmas Tree Staining is another slide staining technique used to microscopically identify sperm. This method is much quicker than Sperm Hyliter. The sperm heads stain red and the sperm tails and other cells stain green. When viewed under a microscope, the sperm heads are fairly easy to spot and differentiate from the surrounding cells. Similar to SpermHyliter™, when identifying sperm heads one looks for the right color, size, shape, and the presence of an acrosome; which is a small unstained part of the sperm head.
The presumptive test used by the BCA to test for saliva is the Phadebas™ test. This test detects the presence of amylase in a sample. Amylase is an enzyme found in high levels in saliva. A Phadebas™ tablet is comprised of a water-soluble starch polymer carrying a blue dye. If the amylase enzyme is present in a sample, it will degrade the starch polymer found in the Phadebas™ tablet, which in turn releases the blue dye.
The test used for urine identification is the detection of Creatinine. Creatinine is found in urine. If creatinine is present, after the addition of various chemicals, a color change from yellow to orange and back to yellow will be observed. A positive sample will turn yellow, orange, and back to yellow while a negative sample will remain yellow the whole time.