Process Used to Test Evidence Items Consistent with Blood and the Kastle-Meyer Test

Forensics: Presumptive blood testing
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The process used to test evidence items consistent with blood
When evaluating forensics evidence for suspected blood, the primary objective is to establish whether the recovered fluid is blood. The recovered liquid is subjected to two identification tests: the presumptive and confirmatory tests to verify whether the sample contains blood.
When a specimen suspected to be blood is brought to a forensic lab, it is first taken through the presumptive test. The test works by screening samples to establish whether it is blood. The tests are primarily color tests where they take advantage of the peroxidase-like properties of blood to observe a color change when the said test is applied (Harris & Lee, 2019, pp. 233). The tests, including phenolphthalein, tetramethylbenzidine, and luminol, are applied directly to the said specimen. A cotton swab, lightly dampened, can also be used. It is placed on the sample for some of its particles to transfer to the swab. The chemicals from a test are then added to the swab, and a color change is observed. Presumptive tests are founded on oxidation-reduction reaction whereby when a reduced dye, in this case, the presumptive test chemical, is applied to blood, a reaction occurs producing oxidized dye and water. The color produced determines whether the suspected sample is presumed to be blood (Harris & Lee, 2019, pp. 233-234).
Once the presumptive test is completed, a confirmatory test is then carried out to determine the identity of the biological material conclusively. Various tests such as DNA, Takaya test, RSID Test for human blood, and the ABDcard HemaTrace test strips are utilized. These tests work by introducing hemoglobin, which acts as an antiserum to the suspected blood evidence, and a visibl...