Chapter 12: Forensic Serology Forensic Science Chapter 12: Forensic Serology

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

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

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

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

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

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

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

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

Serum The liquid that separates from blood when it clots

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

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

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

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

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

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

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

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

Serology The study of antigen-antibody reactions

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

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.

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. http://www.nurseminerva.co.uk/blood1.htm#q5

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

Genotype The combination of genes AO

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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