1. Chapter 12: Forensic Serology
Forensic Science
Chapter 12: Forensic Serology

2. Karl Landsteiner 1901 Figured out how to determine blood type
Won a Nobel Prize

3. Before blood typing
Transfusion recipients often died because the new blood made their blood coagulate.

4. Blood factors Landsteiner created the A-B-O system
By 1937 the Rh factor had been identified
Now, there are more than 100 known blood factors
A-B-O is still the most important for transfusions

5. Importance of blood factors
No two individuals, except identical twins, could be expected to have identical blood factors.
Until the early 1990s, this was the best way to link blood to an individual

6. DNA Deoxyribonucleic acid Molecules that carry genetic information
Double stranded in the shape of a double helix

7. DNA Regions of DNA are now used to match blood to individuals
More on this in chapter 13

8. Plasma The fluid portion of unclotted blood Mostly water
55% of blood content

9. Cells in blood 45% of blood content Erythrocytes - red blood cells
Carry oxygen to body tissues and remove carbon dioxide
Leukocytes - white blood cells
Fight infections
Platelets
Responsible for clotting

10. Serum
The liquid that separates from blood when it clots

11. Antigens
Chemicals on the surface of red blood cells that give them their blood type
Usually proteins
Stimulates the body to produce antibodies against it

12. Antibody A protein that destroys or inactivates a specific antigen
Found in blood serum

13. Blood types Type A Type B Type AB Type O Has A antigens Has B antigens
Has A and B antigens
Type O
Has neither A nor B antigens

14. Rh factor Also known as the D antigen Rh+ blood has the antigen
Rh- blood doesn’t

15. Fundamental principle of blood typing
For every antigen there exists a specific antibody
Anti-A is for the A antigen
Any antibody will only react with its specific antigen and no other

16. Antiserum Blood serum in which there are specific antibodies
Serum from type A blood contains Anti-B
Serum from type B blood contains Anti-A
Serum from type AB blood contains neither Anti-A or Anti-B
Serum from type O blood contains both Anti-A and Anti-B

17. Agglutination
The clumping of red blood cells by the action of an antibody
Each antibody is bivalent – it can attach itself to two different cells

18. Why transfusions failed before blood typing
Example:
Type B blood is given to a person with type A blood
The anti-A antigens in the type B blood attach to the A blood cells
They clump together
The person dies

19. Serology
The study of antigen-antibody reactions

20. Blood typing
Blood of unknown type is mixed with a known antiserum and checked for agglutination
Anti-A Serum + whole blood
Anti-B serum + whole blood
Antigen Present
Blood Type + - A B
A and B AB
Neither A nor B O

21. Blood types in the US
Blood type distribution varies throughout the world
In the US, 43% have O blood, 42% have A, 12% have B, and 3% have AB.

22. If type O blood contains anti-A and anti-B then why can it be given to people with type A blood or type B?
In extreme situations type O negative blood would be the best choice for an emergency transfusion, but in all other situations blood should be accurately cross-matched before transfusion. Type O blood contains serum anti-A and anti-B antibodies which potentially could react with the recipient’s blood cells and produce harmful side-effects such as clumping of red cells. However, since most transfusions consist of adding a relatively small volume of donor blood to a larger volume of recipient blood, dilution of the donated antibodies occurs and this reduces the degree of adverse reactions to a manageable or insignificant level.

23. Drug antibodies
Can be produced
Used to test blood and urine for drugs

24. EMIT Enzyme-multiplied immunoassay technique
Can detect even trace amounts of drugs in urine
May give false positives by reacting with chemicals similar to the drugs – other tests are needed

25. Polyclonal antibodies
Antibodies that attack different sites on the same kind of antigen
Produced by injecting animals with antigens
May change over time

26. Monoclonal Antibodies
Identical antibodies that interact with a single antigen site
Require more manipulation after animal is injected with antigen

27. Bloodstain questions Is it blood? Is it human?
Can it be matched to one person?

28. Benzidine color test Formerly used to test for the presence of blood.
Benzidine is a carcinogen
No longer used

29. Kastle-Meyer test Uses phenolphthalein to test for blood
When blood is mixed with phenolphthalein solution and hydrogen peroxide, it turns a deep pink color
Some other substances, like potatoes and horseradish, will also turn pink

30. Hemoglobin In red blood cells Makes them red Carries oxygen
Makes the Kastle-Meyer test work

31. Hemastix Used to test urine for blood Can be used to test bloodstains
Turn green when there is blood

32. Luminol testing Sprayed on objects in a darkened room
If there is blood, it will luminesce (give off light)
Can detect even very diluted blood
Will not interfere with DNA testing

33. Precipitin test Used to determine what animal blood came from
Adding various antiserums (human, dog, cat) to blood samples
If the antiserum causes the blood to precipitate and get cloudy, it was the correct animal.

34. Classic method
Put blood sample on top of human antiserum in a capillary tube.
If it is human blood, a cloudy ring or band will form where the two substances meet

35. Gel diffusion
Antibodies and antigens will move towards each other on an agar-gel coated plate
They are placed in separate spots on the plate.
If they move towards each other and form a precipitin line, then they match

36. Precipitin test Very sensitive Blood can be diluted or old
Has been successful on mummies

37. Individualizing blood
Blood type
Enzymes
Proteins that have important functions in the body’s chemical reactions

38. Polymorphism The existence of more than one form of a genetic trait
Polymorphic enzymes exist in different forms

39. Iso-enzymes
Multiple forms of an enzyme having the same or very similar activities

40. Example: PGM Not everyone has the same PGM iso-enzymes
3 variations
Helps reduce the number of possible matches

41. Using enzymes on bloodstains
Only the ones that survive drying and aging are useful
The more factors a serologist can identify, the better they can narrow down a sample

42. Bloodstain patterns
Factors that can help interpret and reconstruct events
Location
Distribution
Appearance
Position
Shape
Analysis requires carefully planned control experiments

43. Surface texture
Patterns and matches are only valid if identical surfaces are used
Hard and less-porous surfaces result in less spatter

44. Direction of travel Can be determined from stain’s shape
Pointed end always faces direction of travel

45. Impact angle Can be determined on a flat surface
Measure circular distortion
Right angles produce circular drops
As the angle decreases, the elongation increases

47. Origin of blood spatter
Draw straight lines through the long axis of several drops
Where the lines meet is where the blood came from

48. Genes Control all the antigens and enzymes A unit of inheritance
A DNA segment on a chromosome

49. Chromosomes Threadlike structures in the cell nucleus Hold genes
Made of DNA and proteins
Human cells contain 46 chromosomes in 23 pairs

50. Reproductive cells Contain only 23 chromsomes Egg – female cell
Sperm – male cell
Zygote – combined egg and sperm

51. Sex chromosomes X chromosome – female Y chromosome – male
Shorter than X
The mother always contributes an X chromosome. (females are XX)
The father can contribute an X or a Y. (males are XY)

52. Locus The position a gene occupies on a chromosome
Genes for the same trait from the two parents are next to each other

53. Alleles Alternative forms of genes that control the same traits
Example: blood type has A, B, and O alleles

54. Homozygous
A gene pair of two similar genes
AA or BB or OO

55. Heterozygous
A gene pair of two different genes
AO or BO or AB

56. Genotype
The combination of genes AO

57. Phenotype
What the trait looks like
Type A blood
Could be AA or AO

58. Punnet squares
Predict the possible genotypes and phenotypes of offspring
Examples: father is AO, mother is AB
Father is OO, mother is BO
No gene can appear in a child unless it is present in at least one of the parents

59. Paternity testing Usually civil, not criminal cases
Involves blood factors other than just blood type
Now use DNA

60. Locating semen stains Sometimes you can see it easily
If not, use the acid phosphatase color test

61. Acid phosphatase
Enzyme present in seminal fluid in great concentration
Up to 400 times greater than other bodily fluids
Can be tested with various solutions, with or without UV light
Some other substances – fruits and veggies, fungi, contraceptive creams, and vaginal secretions may give positive results, but not as fast or not as strong

62. Spermatozoa
Sperm
Can be seen through a microscope – means the stain was definitely from semen

63. Locating sperm in a stain
Put the fabric in a little water and stir
Some sperm will come off in the water and can be seen under the microscope
Sperm can be bound tightly to fabric
Sperm are very brittle when dry – can be easily destroyed

64. Medical abnormalities
Oligospermia
Low sperm count
Aspermia
Absence of sperm (sterility)
Natural or after a vasectomy

65. Semen without sperm
Can still be identified as seminal fluid using a protein called p30 or PSA (prostate specific antigen)
Unique to seminal fluid
Detected with antibodies

66. Rape evidence Semen is not enough
Presence just means there was sex
Absence could mean a condom was used
Bruises or bleeding indicate violence
Possible transfer of physical evidence
Blood and semen
Hairs and fibers

67. Protecting evidence
Preserve all outer- and undergarments in paper bags
Have the victim stand over a large piece of paper when disrobing to collect loose foreign material
Bedding or other objects from the scene may be collected as evidence

68. Medical examination As soon as possible
By trained professional (nurse or doctor)
Pubic combings
For foreign hairs
Pubic hair reference samples
Cut 15 – 20 hairs at the skin line

69. Vaginal swabs and smear
When warranted by case history
Two simultaneous swabs – let dry
Two more swabs are smeared on slides – let dry
Rectal swabs and smear
When warranted
Two simultaneous swabs, one kept and one smeared – let dry
Oral swabs and smear
One swab for buccal area, one for gumline
Both swabs get smeared on one slide
Let dry

70. Head hairs Blood sample Fingernail scrapings All clothing Urine sample
At least 50 hairs from different areas of the heat - cut at skin line
Blood sample
DNA and toxicology testing
Fingernail scrapings
Use dull object to collect debris from under nails
All clothing
Urine sample
Drug testing

71. Saliva samples Can be used for DNA
Recovered with a damp swab followed by a dry swab

72. Collected from suspect
Clothing
Victim’s DNA may be present in underwear
Pubic hair combings
Pulled head and pubic hair reference samples
Penile swab if within 24 hours of assault
Blood sample or buccal swab for DNA

73. Testing for sperm in the victim
Motile sperm last for 4 – 6 hours
Requires immediate examination of vaginal smear
Nonmotile sperm can last for 3 – 6 days.
Intact sperm (with tails) usually only last 16 hours, but have been found as late a 72 hours later
Seminal acid phsophatase can last for 48 hours
p30 can last for 24 hours