Forensic Serology

Chapter 8

Blood Components

Plasma--fluid part of blood unclotted blood

Erythrocytes—hold hemoglobin and transport oxygen

Leukocytes—immune cells

Platelets--clotting Serum—yellow fluid

that remains after clotting of blood, mostly water + dissolved substances (proteins, ions, etc)

Antigen and Antibodies

Blood Type A has A antigens and B antibodies

Blood Type B has B antigens and A antibodies

Blood Type AB has both A and B antigens and no antibodies

Blood Type O does not have any antigens but both A and B antibodies

Positive blood has Rh(D) antigens = Rh+

Negative blood does not have Rh(D) antigens but has D antibodies = Rh-

Serology

Positive blood will agglutinate with Anti D serum

Negative blood will not agglutinate with Anti D serum

A blood will agglutinate with Anti A serum

B blood will agglutinate with Anti B serum

AB blood will agglutinate with both anti A and anti B serum

O blood will not agglutinate with anti A or anti B

http://www.youtube.com/watch?v=E0d5Qx42vmQ

Paternity Testing with Blood Type

A Blood Type—AA or AO B Blood Type—BB or BO O Blood Type—OO AB Blood Type—AB Parent gives each

offspring one of two alleles

Immunoassay techniques

Used to detect drugs in blood and urine

Animals are injected with proteins with drug antigens—animal makes drug detecting antibodies that can be harvested

Presumptive drug testing with these cultured antibodies can be used to detect opiates, cannabinoids, cocaine, amphetamines, phencyclidine, barbituates and methodone

Producing Antibodies

Radioimmunoassay (RIA)—uses radioactive tags to find drugs

Enzyme-Multiplied Immunoassay Technique (EMIT)—fast and used with urine; adds antibodies to urine that bind to specific drugs

Polyclonal and Monoclonal Antibodies—animals produce many different antibodies when exposed is polyclonal; scientists need one kind of antibody (monoclonal; fused with cancer cell to make hybridoma cell

Blood Stain Analysis

3 Questions Is it blood? Is it human? Can it be matched

closely to a particular person?

Presumptive Color Testing

Benzadine color test—use has been reduced because it is a carcinogen; measures for presence of hemoglobin

Kastle-Mayer—uses phenolphthalein as an indicator, and hydrogen peroxide to cause the conversion of catalase to give pink color; will test positive with samples with catalase (animal and some plant material)

http://www.youtube.com/watch?v=6Ex0Fd_PDhU

Luminol

Presumptive blood test Reaction with blood

emits light that can be seen in darkened area

Sprayed on area, turn dark, emits blue light

http://www.youtube.com/watch?v=hbEHvRrfqrc

Microcrystalline Tests

Takayama test Teichmann tests Add chemicals to blood

that causes hemoglobin-containing crystals to form

Susceptible to contaminants and less sensitive that color tests

Precipitin Test

Used to determine if blood stain is human or from animal

Grow antibodies to human blood in rabbit; use antibodies to test for presence of human antigens; Human antiserum

Rabbits can be used to make antibodies against various animal bloods as well

Gel Diffusion

Use agar gel—antibodies and antigens come together in medium plate

Blood and human antiserum are loaded into wells

Precipitant forms if blood is human between two wells

Blood Spatter

Important Blood Qualities to Interpret Blood Spatter Surface texture—more

spatter with softer, porous material

Direction of travel—pointed end faces direction of travel

Impact angle—right angle yields circular stain

Origin of spatter—draw lines through many spatter points; point of intersection is origin of spatter

http://www.youtube.com/watch?v=Od8YuwUT794

Forensic Analysis of Semen

Tests for Presence of Semen Acid Phosphatase Stain—acid

phosphatase is made by the prostate gland and added to semen during ejaculation; presence can be detected by acidic sodium alpha napthylphosphate and fast blue dye or 4-methyl umbelliferyl phosphate (will fluoresce)

Microscopic examination—look for presence of sperm cells

Prostate specific antigen—polyclonal antibodies grown in rabbits used to bind to p30 protein or prostate specific antigen

Rape Evidence Collection

Rape Kit Collection from victims Hair samples: head,

pubic, body Body opening swabs:

vagina, anus, mouth Blood sample Fingernail scrapings All clothing Urine sample

Collected from male suspects All clothing Hair: head, pubic, and

body Genital swab Blood sample Cheek cells