1. Criminalistics Chapter 12
Forensic Serology
Criminalistics
Chapter 12

2. Karl Landsteiner
First person to recognize that all human blood is not the same
Blood is distinguishable by its’ group or type
Now called the A-B-O System
Important because using the wrong blood cause instant death for those receiving transfusions
Today there are more than 100 different blood factors known

3. Blood as Identification
In theory, no two individuals, except for identical twins, could have the same combination of all individual blood factors (not just blood types)
Blood factors are controlled genetically and have the potential of being a distinctive feature for personal identification
Important in serious crimes where blood is found at a crime scene—homicides, assaults, and rape.

4. Blood as Evidence
Blood typing not so useful anymore because of DNA technology
Scientists can now characterize biological evidence by selecting regions of our DNA

5. The Nature of Blood
Blood: complex mixture of cells, enzymes, proteins, and inorganic substances
Plasma: the fluid portion of blood
Mostly water
55% of blood content
The other 45% is made of solid particles

6. The Nature of Blood Erythrocytes: red blood cells; found in plasma
Leukocytes: white blood cells; found in plasma
Platelets: clotting factor; found in plasma
Serum: the liquid that separates from the blood when a clot is formed

7. Important Parts for Forensic Science
Red Blood Cells—because of their importance in blood typing
Serum—because of its’ importance in carrying antibodies

8. Red Blood Cells and Blood Types
Protein resides on the Red Blood Cell called antigens
Antigens give blood-type characteristics to the Red Blood Cells
ABO and Rh systems are the most important blood types

9. Antigens and Blood Types
Type A Blood has Antigen A on the surface of the Red Blood Cell
Type B Blood has Antigen B on the surface of the Red Blood Cell
Type AB Blood has both Antigen A and Antigen B on the surface of the Red Blood Cell
Type O Blood has neither Antigen A nor Antigen B on the surface of the Red Blood Cell

10. Distribution of Blood Types in US
Type O Blood is the most prevalent with 43%
Type A Blood is the next most common with 42%
Type B Blood is less common with 12%
Type AB Blood is the most rare type with 3%

11. Rh Factor or D Antigen
Blood that contains the D Antigen is referred to as Rh +
Blood that does not contain the D Antigen is referred to as Rh -

12. A, B, D—that determines a person’s blood type.
In routine blood typing, it is the presence or absence of the three antigens—
A, B, D—that determines a person’s blood type.

13. Fundamental Principle of Blood Typing
Serum contains proteins known as antibodies
For every antigen, there is a specific antibody that reacts against it.
Anti-A reacts against antigen A
Anti-B reacts against antigen B
When antibodies react against its’ specific antigen, agglutination or clumping of RBCs occur.

14. Blood Type Antigens on RBCs Antibodies in Serum
Antigen A
Anti-B B
Antigen B
Anti-A AB
Antigen A and Antigen B
Neither Anti-A nor Anti-B O
Neither Antigen A nor Antigen B
Both Anti-A and Anti-B

15. What is Serology?
The term serology refers to a broad scope of laboratory tests that use specific antigen and serum antibody reactions.
Blood typing falls into this category.

16. Forensic Characterization of Blood Stains
Important Questions:
Is it blood?
From what species did the blood originate?
If the blood is human, how closely can it be associated with a particular individual?

17. Preliminary Determination of Blood
Sample tested with phenolphthalein
Turns deep pink color Positive for blood
Also known as the Kastle-Meyer Test
Use of Hemastix
When moistened with distilled water and placed in contact with stain, a bright green color indicates blood.

18. Preliminary Determination of Blood
Luminol Test
Produces light if blood is present in a darkened area
Extremely sensitive: can detect stains diluted up to 300X
Will not interfere with any subsequent DNA testing

19. Is it human blood? Precipitin Test:
Human blood is inserted into animal (rabbit)
Rabbits produce antibodies to react against the human blood
Blood is drawn from rabbit that contains the human antibodiesproduces human antiserum
Unknown blood sample, if human, will react with the human antiserum from the rabbit by forming a precipitate

20. Is it human blood? Gel Diffusion and Electrophoresis
Antibodies and antigens will move toward each other on an agar gel plate or in an electrophoresis chamber
Forms a precipitate where the human antibodies and antigens meet
No precipitate? Unknown sample is not human blood

21. Effectiveness of Tests for Human Blood
Precipitin Test:
Very sensitive and requires only a very small amount of blood
Works on very old samples
Even in washed items blood may be detected

22. Stain Patterns of Blood
Important Factors:
Location of stains
Distribution of stains
Appearance of stains
All factors are important in interpreting and reconstructing the events of a crime scene.

23. Blood Pattern Interpretation
Important Factors:
Surface Texture
Harder and less porous surfaces produce less spatter results
Direction of travel
Determined by the shape of the stain
Pointed end of stain always points in the direction of travel

24. Blood Pattern Interpretation
Important Factors:
Angle of Impact
Right angle of impact produces a circular drop stain
As angle decreases, the blood drop becomes more elongated
Origin of Blood Spatter
Can be determined by drawing lines or connecting strings through blood stains

25. Principles of Heredity
Antigens and enzymes are genetically controlled
Genes: responsible for transfer of hereditable material
Genes are found on chromosomes, which are found in the nucleus of every cell

26. Principles of Heredity
Human Cells contain 46 chromosomes with the exception of the egg and sperm, which contain only 23.
23 of these chromosomes are inherited from mother
23 of these chromosomes are inherited from father

27. Sex Chromosomes X-Chromosome: Female Sex Chromosome
Y-Chromosome: Male Sex Chromosome
XX individuals are female
XY individuals are male

28. Genes Come in Pairs
The position a gene occupies on a chromosome is called a locus.
Genes for the same trait are located at the same locus on both the mother and the father’s chromosomes.

29. Genes Come in Pairs
Alternative forms of genes that influence a given characteristic are called alleles.
Father: allele for brown eyes
Mother: allele for blue eyes

30. Gene Pairs Made up of two similar genes AA: Homozygous
“Homo” means the same
Aa: Heterozygous
“Hetero” means different

31. Blood Types are Genetic
A and B Blood Types are Dominant
Dominant: Characteristic is shown
Blood Type O is Recessive
Recessive: Characteristic is hidden
Recessive characteristics only appear when both alleles are recessive
Homozygous recessive OO

32. Phenotype V. Genotype Phenotype: individual’s outward characteristics
Genotype: individual’s pair of allele genes together
Example:
Phenotype Genotype
Type B Blood Could be BO or
BB depending
on parents

33. Genotype of a child with Type B Blood must be BB
Punnett Squares
Mother: AB Father: BB B B AB BB A
Genotype of a child with Type B Blood must be BB B

34. Paternity Tests
No blood group can be present in a child without being present in one of the parents
Paternity tests can be resolved in this way unless disputed fathers have the same blood type
Paternity tests can also be determined by using DNA testing

35. Forensic Characteristics of Semen
Normal male can ejaculate ml of seminal fluid
Each ml contains 100 million or more spermatozoa

36. Testing for Semen Stain must be located and collected
Acid Phosphatase Color Test
Purple color indicates the presence of semen
Spermatozoa Test
Semen is diluted with water and dried on filter paper
Microscopic examination looks for spermatozoa

37. Rape Evidence Presence of seminal fluid
Physical injuries such as bruising or bleeding confirms a violent sexual assault took place
Transfer of physical evidence—blood, semen, fibers, and hair—are usually present

38. Collection of Rape Evidence
All outer and undergarments are collected and packaged separately in paper bags
Trace evidence is collected by standing on a clean sheet while removing clothing
Bedding may be recovered if seminal stains are present
Medical Examination of the victim

39. Medical Examination of Victim
Pubic Combings
Pubic Reference Samples from victim
Vaginal swabs and smear
Rectal swabs
Oral swabs
Head hairs
Blood sample
Fingernail scrapings
All clothing
Urine specimen

40. Medical Examination of Suspect
All clothing
Pubic hair combings
Pulled head and pubic hairs for reference samples
Penile swab
Blood sample or buccal swab