1. Testing for Presence of Blood Evidence
Notes 3.3

2. Is it Blood?
Hemastix
Designed to test for the presence of blood in the urine, but can have applications in forensic investigation
The test will turn green if the stain is in fact blood
Destructive test--blood that comes into contact with the hemastix cannot be used to extract DNA

3. Is it Blood? Kastle-Meyer Test
A nondestructive test, i.e., DNA can be recovered from the blood treated with K-M protocol. It works best on old blood stains.
The hemoglobin in the stain will oxidize and react with the phenolphthalein indicator. The stain is mixed with phenolphthalein and then hydrogen peroxide.
The test will turn pink if the stain is blood
The enzymes in some vegetables (tomato, potato, cucumber, horseradish) can cause a false positive
Must be read within 30 seconds

4. Is it Blood?
Luminol
The hemoglobin in the stain will oxidize and activate the chemoluminescent properties of the Luminol.
Luminol is an aerosol sprayed on the stain. Results must be observed within seconds.
The test will produce blue or green light if the stain is in fact blood
Nondestructive test, i.e., DNA can still be recovered from the sample (but can’t do blood typing)
Luminal tests do not indicate the amount or distribution of blood. (see page 249)

5. Is it Human Blood?
Precipitin Test (Ouchterlony double immunodiffusion) (see page 339)
Human blood antibodies can be created by injecting animals with human blood. This is also done with human blood types (ABO).
The bloodstain is placed on top of antiserum containing the antibodies
The test will form a cloudy ring if the stain is human blood
Destructive test

6. Science Behind the Precipitin Test

7. Whose blood is it? Antiserum Tests
Human blood antibodies are created against type A and type B antigens (from animal immune systems)
The bloodstain is mixed with a solution containing the antibodies
The RBCs will agglutinate (a positive test) if the antigens are present
Destructive test

8. Figure 8-5 

9. Figure 8–1  

10. Agglutination
Antiserum A will agglutinate with blood containing antigen A
Why does the image to the right indicate Type A and not Type AB?

11. Agglutination

12. Identify the Blood Type!
Person 1
Person 2
Person 3
Person 4 AB B A O

13. Identify the Blood Type!

14. 12 Testable Possible Results

15. Unlike RBCs, White blood cells contain DNA