Introduction to Bodily Fluids and Presumptive Tests

Question 1

What is the purpose of EDTA in blood?

Answer 1

• For a number of forensic tests we need to keep the blood sample whole and store the samples in vials containing EDTA (Ethylenediaminetetraacetic acid)
• EDTA preserves the DNA in blood, preventing the blood from coagulating.

Question 2

What does the Kastle Mayer test for, and how is it conducted?

Answer 2

The KM test is a presumptive test for blood.

It is performed by adding ethanol, phenolphthalein and hydrogen peroxide to the suspected blood stain.

If the presumptive test is postive, the KM test will turn pink/purple.

If the presumptive test turns pink/purple after adding the phenolphthalein, there is a false positive.

Question 3

What is saliva?

Answer 3

• Saliva is a product of the exocrine glands. It is a secretion released to the outside of the body through ducts.
• It is a very common source of DNA, and can be obtained from bite marks and spit.

Question 4

What is the ELIZA test and what is the Phadebas test?

Answer 4

• The ELIZA test is most commonly encountered for the presumptive testing of the presence of saliva staining.
  
  • The same technique is used to determine the presence of drugs and drug screening.
• The phadebas test is a presumptive test for the presence of saliva.

Question 5

How is the Phadebas test conducted?

Answer 5

The Phadebas test paper is impregnated with degradable starch microspheres and blue dye.

1. The region of possible saliva staining is wetted and then swabbed with a cotton swab.
2. The swab is then wrapped in phadebas paperand placed under weight.
3. The amylase in the saliva digests the starch and the dye will run.