1. Identification and Characterization of Blood and Bloodstains

2. Summary Introduction to Blood Identification of Blood as Blood
Determining Species Origin of Blood
Identifying Humans using Blood

3. Introduction to Blood What you should already know:
It’s that red stuff that comes out of your fingers following a kitchen accident.
Lets look at blood.

4. Introduction to Blood RBC = no DNA; WBC = yes DNA
All blood cells have blood groups on outside of cell.

5. Introduction to Blood
ABO blood groups found on outside of cell

6. Introduction to Blood
ABO blood groups found on outside of cell

7. Red blood cells contain hemoglobin
Hemoglobin picks up and drops off oxygen

8. Forensic Analysis of Blood
Visual examination of evidence
Presumptive screening test (Is it blood?)
Confirmation test (Seriously, is it blood?)
Determine species origin (human blood?)
Identify the blood (whose blood is it?)

9. Forensic Analysis of Blood
Visual examination of evidence
Presumptive screening test (Is it blood?)
Confirmation test (Seriously, is it blood?)
Determine species origin (human blood?)
Identify the blood (whose blood is it?)

10. Forensic Analysis of Blood
Visual examination of evidence
Presumptive screening test (Is it blood?)
Confirmation test (Seriously, is it blood?)
Determine species origin (human blood?)
Identify the blood (whose blood is it?)

11. Presumptive Screening Tests
Negative result means the questioned stain is not likely blood
Positive result means the questioned stain is likely blood

12. Presumptive Screening Tests
Presumptive tests produce a color reaction or release of light
Tests rely on catalytic properties of blood (hemoglobin presence)

13. Presumptive Screening Tests
Color Tests
Remember, other non-blood substances might catalyze the reaction also.
Chemical Oxidants
Plant materials
False Positive – A positive result given by a substance that is not blood.

14. Presumptive Screening Tests
5 Types of Color Tests
Benzidine
Phenolphthalein
O-Tolidine
Tetramethylbenzidine (TMB)
Leucomalachite Green (LMG)

15. Presumptive Screening Tests
Benzidine
Positive result = blue color
Carcinogen (cancer causing) in 1974
No longer used by most scientists

16. Presumptive Screening Tests
Phenolphthalein
Positive result = pink
Some other substance produce colors other than pink (not blood)
Still used today

17. Presumptive Screening Tests
O-Tolidine
Positive result = blue
Similar to benzidine; still carcinogenic as it can be metabolized to benidine
No longer used; gradually replaced by TMB

18. Presumptive Screening Tests
Tetramethylbenzidine (TMB)
Positive result = Blue-green
Most common test for blood
Rub stain with moist swab
Add TMB
Add peroxidase
Look for quick blue color

19. Presumptive Screening Tests
Tetramethylbenzidine (TMB)
Positive result = Blue-green
Most common test for blood
Rub stain with moist swab
Add TMB
Add peroxidase
Look for quick blue color

20. Presumptive Screening Tests
Leucomalachite Green (LMG)
Positive result = Green
Not as sensitive as TMB or specific as phenolphthalein

21. Presumptive Screening Tests
Chemiluminescence and Fluorescence
Chemiluminescence – light is emitted as a product of the chemical reation
Fluorescence – light is emitted when a substance is exposed to a UV light

22. Presumptive Screening Tests
Chemiluminescence and Fluorescence
More sensitive than color tests
May damage blood stain (no blood/DNA typing)
Used to locate and define areas of blood
old blood stains
cleaned floor

23. Presumptive Screening Tests
Luminol
Method similar to color test
Luminol is combined with oxidant and sprayed over area thought to contain blood
Emits a blue-white to yellow green glow

24. Presumptive Screening Tests
Luminol

25. Presumptive Screening Tests
Fluorescein
Fluorescein is combined with oxidant and sprayed over area thought to contain blood
Fluoresces when treated with a UV light
Fluorescein includes a thickener; this makes it more effective on vertical surfaces
Study showed no interference with DNA analysis

26. Presumptive Screening Tests
Fluorescein

27. Forensic Analysis of Blood
Visual examination of evidence
Presumptive screening test (Is it blood?)
Confirmation test (Seriously, is it blood?)
Determine species origin (human blood?)
Identify the blood (whose blood is it?)

28. Confirmatory Tests
Due to the possibility of false positives with the presumptive tests, confirmatory tests are necessary
Confirmatory tests involve making crystals that detect the presence of hemoglobin

29. Confirmatory Tests Teichmann Test and Takayama Test
Small amount of blood added to microscope slide
Chemical solution is added
Slide is heated to form crystals
Crystals viewed under microscope

30. Forensic Analysis of Blood
Visual examination of evidence
Presumptive screening test (Is it blood?)
Confirmation test (Seriously, is it blood?)
Determine species origin (human blood?)
Identify the blood (whose blood is it?)

31. Species Origin Most methods test for serum proteins
Serum proteins are found in all animals, but are slightly different
Species ID methods based on antigen/antibody interactions

32. Species Origin Antigen = serum protein
Antibody = produced when foreign serum protein is detected
Certain antibody will only attach to one species’ serum protein

33. Forensic Analysis of Blood
Visual examination of evidence
Presumptive screening test (Is it blood?)
Confirmation test (Seriously, is it blood?)
Determine species origin (human blood?)
Identify the blood (whose blood is it?)

34. Genetic Markers in Blood
If a stain is blood, and it is human blood, then whose is it?
Blood Group Markers
Protein/Enzyme Markers
DNA