Biological evidence presumptive tests from (L2)

Question 1

test for semen

Answer 1

ACP (acid phosphatase) test. This enzyme is found at high levels in semen samples and semen sample is swabbed or placed in damp blotting paper to react with the solution (sodium alphanapthylphosphate and fast blue B) to indicate the presence of semen in the scene. If positive, it indicates violet.

Question 2

test for saliva

Answer 2

Phadebas test. This tests for alpha-amylase in our saliva, which is the main enzyme found in our saliva that breaks down sugar. Turns blue if positive. This could indicate that maybe saliva is present, because amylase is also found in other body fluids, and at lower levels.

Question 3

three presumptive tests for blood

Answer 3

1. COMBUR test. Catalytic reaction of haemoglobin from blood sample with the peroxide substrate of test. If positive for blood, it turns the indicator from yellow to green. This is sensitive rather than specific
2. KASTLE-MEYER. Uses phenolphthalein to react with the possible presence of haemoglobin. Turns colorless to pink. Kastle-MEyer is more specific, less sensitive.
3. Luminol: reacts with the iron in haemoglobin. Requires dark light because the indicative presence of blood using this solution is luminescence. It is non-specific which means other substances can cause a reaction, e.g. horseradish, bleach, and copper.