1. Identification Using Blood Groups
Forensic Serology
Identification Using Blood Groups

2. Forensic Serology
Serology – term used to describe a broad range of laboratory tests using reactions of blood serum and body fluid
The serology section of a forensic laboratory may deal with any or all of the following:
blood typing
characterization of unknown blood
stain patterns for crime reconstruction
paternity testing
semen identification in rape cases
DNA techniques used for identification

3. The Composition of Blood
Blood is a mixture of many components:
cells inorganic substances (salts)
enzymes water
proteins
55 % of blood content is plasma – mostly water and substances dissolved in it
Most of the solid materials (by weight) are cells
red blood cells, RBCs (erythrocytes)
white blood cells (leukocytes)

4. How blood evidence is collected
Most items
Collected in clean, unused paper containers such as packets, envelopes, and bags.
Blood pool –
collect with gauze pad or clear cotton. Let air dry and refrigerate of freeze within 48 hours.
Dried blood –
wrap object in clean paper and place in paper bag.
Small object: send whole object in.
Large object: cover with paper and tape down or scrape it off with a knife.

5. Preserving Moist or wet biological evidence
- Blood, body fluids, plants, etc.
1) Placed in clean, unused plastic containers at the scene and transported back to an evidence receiving area
Only if the storage time in sealed plastic is less than two hours
To prevent contamination of other evidence
2) Must be removed and allowed to completely air dry
3) Repackaged in a new, clean, unused, dry paper container
Reason for no more than 2 hours
Moisture allows the growth of microorganisms that can destroy or alter evidence

6. Forensic Characterization of Bloodstains
Three questions that must be answered by the forensic investigator:
1) Is it blood?
Benzidine Test
Kastle-Meyer Test
Hemastix (o-tolidine, TMB)
Luminol Test
2) Is it human blood?
Precipitin Test
3) Can it be associated with an individual?

7. Benzidine and Kastle-Meyer Color Test Kastle-Meyer Color Test
Preliminary Color Tests
Benzidine Color Test
Benzidine is carcinogen so not used as often
Benzidine + Blood Stain + Hydrogen peroxide
= pink color
Kastle-Meyer Color Test
- phenolphthalein
- Phenolphthalein + Bloodstain + Hydrogen peroxide

8. Human or Animal origin? Precipitin Test
• Combine human antiserum and human bloodstain there should be agglutination
• Requires only small amount of blood
• Dried bloodstains as old as years work
Procedure:
1) Rabbits injected with human blood make antibodies in their serum
2) They are bled and the serum recovered
3) The serum is called human antiserum, because it will react to human antigens
4) It will cause coagulation when mixed with human blood 

9. Precipitin Test

10. Luminol Test Reacts with blood to produce luminescence
• Sensitive to blood that have been diluted up to 10,000 times
• Destroys many important blood factors
Iron present in any blood in the area catalyzes the chemical reaction that leads to the luminescence revealing the 

11. Luminol
Red blood cells contain hemoglobin (Hb) – the protein responsible for transporting oxygen
Each Hb contains four iron (Fe) containing hemes
Heme structure

12. Luminol
Red blood cells contain hemoglobin (Hb) – the protein responsible for transporting oxygen
Each Hb contains four iron (Fe) containing hemes
Heme structure

13. Hemastix© tests strips to detect blood in urine.
But these strips can be used at a crime scene to detect fresh or dried blood
It detects the peroxide-like activity of hemoglobin.

14. Blood Antigens
On the surface of red blood cells are chemical structures (proteins) called antigens
The presence of antigens allow a living system to recognize foreign biological substances
Antigens also impart specific characteristics to the red blood cells. These characteristics can be partly used to identify individuals
Human red blood cells have more than 15 different antigen types that have been discovered

15. Blood Typing
Blood typing involves determination of the antigens present on an individual’s RBCs
The two most common blood typing systems used are the A-B-O method and the Rh method
type A blood – contain “A” antigen on RBCs
type B blood – contain “B” antigen on RBCs
type AB blood – contains both A and B antigens
type O blood – contain no A or B antigens
Rh+ blood – contain Rh antigen
Rh- blood – no Rh antigen

16. Blood Typing
Blood also contains antibodies – proteins that recognize and bind to certain, specific antigens
Blood Type Antigens on RBC Antibodies
A A anti-B
B B anti-A
AB AB none
O none both A & B

17. Blood Typing
When blood containing a specific antigen is mixed with blood containing the corresponding antibodies, the blood clots
The clots can then be removed by the host system

18. Blood Typing
Human serum containing specific antibodies can be purchased
Separately mix a drop of unknown blood sample with drop of each anti-serum
Reaction between blood and anti-serum
No reaction between blood and anti-serum

19. Blood Typing Example
A sample of unknown blood is mixed with three anti-sera samples:
Tube 1 (Anti-A): No reaction
Tube 2 (Anti B): No reaction
Tube 3 (Anti Rh): Cloudy reaction
In terms of the A-B-O and Rh systems, what type blood is the sample?
The ABO antigens are not confined to RBC; 80% of Americans are secretors, found on other cells

20. Blood Typing Example
A sample of unknown blood is mixed with three anti-sera samples:
Tube 1 (Anti-A): No reaction
Tube 2 (Anti B): No reaction
Tube 3 (Anti Rh): Cloudy reaction
In terms of the A-B-O and Rh systems, what type blood is the sample?
The ABO antigens are not confined to RBC; 80% of Americans are secretors, same antigens found on other cells
O positive

21. Blood Splatter Analysis
Categories of Bloodstains:
Passive (dripping)
Transfer (smearing)
Projected
Projected Bloodstains occur in shootings, trauma from blunt weapons, hacking, or slashing attacks.

22. Projected Bloodstain Analysis
Two Important Determinations:
a. direction of splatter
b. angle of impact with surface
sin  = (width drop / length drop)

23. Spines, Satellites, Elongation Tails
Splines
Satellites
Elongation Tails
Satellites