1. From what species did the blood originate?
Blood & Heredity
If blood is suspected, a criminalist must answer the following questions:
Is it blood?
From what species did the blood originate?
If the blood is human, how closely can it be associated with a specific person?

2. Kastle-Meyer color test
Preliminary color test, tests for the presence of hemoglobin in blood (peroxidase)
When a bloodstain, K-M reagent, and hydrogen peroxide are mixed, it produces a deep pink color
Its not specific for blood, potato and horseradish will turn the reagent pink, but a positive K-M test is still highly indicative of blood
The Kastle-Meyer blood test is sensitive to dilutions of one part blood to ten thousand parts water

3. Hemastix strips
Urine dipstick is useful as a presumptive field test for blood (peroxidase activity in hemoglobin)
Strip can be moistened with distilled water and placed in contact with a bloodstain
The appearance of a green color change indicates the presence of blood
Positive reaction will take place in less than 30 seconds
Screens for minute amounts of blood and will respond to trace levels of hemoglobin
Detecting blood at such dilute concentrations is approximately equivalent to detecting 5-20 intact red blood cells per microliter of fluid.

4. Luminol The reaction of luminol with blood produces light
After spraying luminol, darken the room, any blood will produce a faint blue glow called luminescence
It is extremely sensitive
May reveal blood traces or patterns that could have gone unnoticed in lit areas
It does not interfere with DNA testing

5. Precipitin Test
Once characterized as blood, need to determine whether its human or animal
The standard test is the precipitin test
Animals are injected with human blood, antibodies form that react with the invading human blood antigens
Investigator recovers antibodies by bleeding the animal and isolating the serum
This serum has antibodies that reacted with the human antigens (human antiserum)
Same thing can be done with any animal to produce dog antiserum, cat antiserum, etc.

6. Performing precipitin tests on blood
Place an amount of human antiserum that was made in the rabbit in a test tube
Layer bloodstain on top of that
If it is truly human blood, the human blood will react with the antibodies in the antiserum and form a cloudy band between the two liquids

7. Gel Diffusion
Antibodies and antigens diffuse or move toward one another on a plate coated with a gel
The bloodstain and human antiserum are placed in holes opposite each other on the gel
If the blood is human, a line of precipitation forms where the antigens and antibodies meet
Once it is determined that it is of human origin, DNA tests are performed

8. Blood can also be examined microscopically
Bird Blood
Cat Blood
Dog Blood
Fish Blood
Frog Blood
Snake Blood
Blood can also be examined microscopically
Human Blood
Horse Blood

9. Heredity All antigens are genetically determined traits
Inherited from parents and are part of the biological makeup once that person has been conceived
Genetic material is transferred by genes
Genes are located on chromosomes that are located inside the nucleus
Almost all human cells have 46 chromosomes
The only exceptions are the gametes, which are sperm and egg cells, which contain 23 chromosomes

10. Sex Cells Females carry X chromosomes Males carry X and Y chromosomes
When an X sperm fertilizes the female egg, it now contains XX, which is female
When a Y sperm fertilizes the female egg, it now contains XY, which is male
The sperm cell determines the chromosome pair, so males determine the sex of the child

11. There are three alleles (A,B,O)
BLOOD GENETICS
There are three alleles (A,B,O)
The first two are A and B and are co-dominant and produce antigens on the surface of red blood cells
The third allele is O and is recessive
AA for type A
It can exist in heterozygous situations in type A as AO or in type B as BO but is not expressed
Homozygous
BB for type B
When the gene is homozygous OO it is said to be type O
AB for type AB

12. Genotype and Phenotype
A pair of genes makes up the genotype
No known lab test can determine an individual’s A-B-O genotype
A phenotype is a person’s outward characteristic, such as having A blood
This still does not tell whether the genotype is AA or AO
It can only be determined by studying the family history

13. Paternity testing
No blood can appear in a child unless it is present in at least one of the parents
Has important implications in disputed paternity cases, which are encountered in civil, not criminal, cases
Many cases can be solved by comparing the blood types of mother and suspected father
If the father can not be excluded, then all that can be said is that he may be the father because of blood typing, but does not strictly mean he is the father
Further testing, such as DNA, will be required