Presumptive And Confirmatory Tests For The Presence Of Amylase

The commonly used test for saliva in the forensic laboratories are presumptive tests for the presence of amylase, not a confirmatory test, amylase, which is merely a component of saliva. The amylase tests which is usually either the Phadebas test or the starch-iodine radial diffusion test, will indicate a positive result if amylase is present and will also give an indication for the quantity of amylase present. Generally, a strongly positive amylase test is a good indication for the presence of saliva. However, it is important to be aware of what sort of sample is yielding the positive result.
Confirmatory tests for the presence of saliva do exist, but however, there has been some cross-reactivity with other body fluids, so, many labs do not …show more content…
The presumptive test, usually an Acid Phosphatase test is used, it is a quick color change test that indicates that semen might or could be present. However, it is well known that a false positive does exist with this test. Instead it is often reported that a sample is “positive for the presence of semen” even if only one or two sperm cells could be located. This can be somewhat misleading as the presence of a single sperm cell may mean something far different than the presence of a multitude of sperm cells. One of the most common false positives is the vaginal acid phosphatase (VAP). The VAP is present in varying concentrations in the vaginal fluid where pregnant women are known to have higher levels of VAP. Confirmatory tests for the presence of semen include a microscopic examination and identification of spermatozoa as well as the P30 assay. The P30 assay is typically used only when a sample is AP positive, but no sperm can be identified under the microscope. The Green river killer case mainly involves the semen and saliva samples, Gary Leon Ridgway also known as the Green River Killer (suspect), is an American serial killer, convicted of 48 separate