1. Chapter 11; Blood

2. Serology; the study of bodily fluids

3. Separation of blood Living portion of blood is:
Erythrocytes (red blood cells…RBCs)
Leukocytes (white blood cells)
Platelets
Liquid part of the blood with no cells in it is called the plasma.
(Mostly water with salts, ions, proteins.)
Separation of blood

5. BLOOD TRANSFUSIONS were not working!
OUTLAWED IN MOST COUNTRIES IN EARLY 1900’S

6. ABO Blood Typing (Karl Landsteiner – 1901)
A classification of blood: A, B, AB, O
Rhesus monkey factor (Rh) discovered in 1940.
If you have it, you’re Rh+ and if you don’t you’re Rh-

7. Theoretically, no two people have the same combination of blood factors and it should be possible to individualize evidence using blood, but in reality this is not the case.
Testing for every factor on RBCs in not practical, and many factors break down as blood dries and ages.
Blood is still important in forensics because testing can be done on both whole blood and dried bloodstains quickly and inexpensively.

8. Antigens and antibodies

9. Each antibody binds to a specific antigen; an interaction similar to a lock and key.
The antibody destroys
the antigen

11. AGGLUTINATION
THE CLUMPING
TOGETHER
OF RED BLOOD
CELLS

12. Lattes slide method Uses antibody-antigen reactions to test for
blood types

13. Varies by country, ethnic group, etc.

15. Blood typing can be used to:
-show that two samples had different origins (exclude a suspect)
-determine the probability of an individual having a particular blood type

16. What is the probability that an American has type AB- blood?
4/100 x 15/100 = 60/10,000 or 0.6%

17. Blood Tests
Determines whether a substance is blood or not, but does NOT distinguish between human and animal blood.
Hemastix test

18. LUMINOL TEST
LUMINESCES WITH BLOOD OR SEMEN

19. PRECIPITIN TEST Determines if blood is human
An animal (mammal) is injected with sample. If human, animals produce antibodies.

20. Non-mammals
Oval red blood cells with a visible nucleus

21. Mammals
Circular red-blood cells
No nucleus

22. Secretors 80 % of population
Blood type antigens are secreted in bodily
fluids (saliva, semen, perspiration,
gastric and vaginal secretions)

23. Blood enzymes
Proteins that regulate chemical reactions

24. Iso-enzymes Protein components into which enzymes can be separated
(1) PGM – an enzyme that has 10 variations
(2) importance- allows forensic scientists to reduce the number of possible sources

25. BLOOD SPATTER

26. SIZE AND SHAPE OF DROPS ARE AFFECTED BY:
HEIGHT OF FALL
ANGLE OF IMPACT
SURFACE ON WHICH THE DROPS LAND

27. Shape is determined by the impact angle

28. Determination of Impact Angle
Measure the length
and width
of the stain
Determination of Impact Angle

29. Divide the width by the length to get arc sine of the impact angle
Width / Length = arc sine of impact angle
Ex: width = 2.4 cm
length = 3.1 cm
Ratio of width/length =
2.4 cm / 3.1 cm =
.77419

30. Use your calculator to get the impact angle
Enter:
“sin -1 (.77419)”
Answer:
50.7 degrees
50.7
Use your calculator to get the impact angle

31. Blood spatter labs 1. Height of drops vs. drop size
2. Angle of drop vs.
drop shape
3. Surface texture vs. drop size and shape
Blood spatter labs

32. The Nobel Prize in Physiology or Medicine – Educational (Blood type simulation)

33. American Justice; Jeffrey MacDonald