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