Forensic serology
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Forensic Serology. Chapter 8. Blood Components. Plasma--fluid part of blood unclotted blood Erythrocytes—hold hemoglobin and transport oxygen Leukocytes—immune cells Platelets--clotting

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Blood components
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
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-


  • 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


Paternity testing with blood type
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
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
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
Blood Stain Analysis

  • 3 Questions

    • Is it blood?

    • Is it human?

    • Can it be matched closely to a particular person?

Presumptive color testing
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)



  • Presumptive blood test

  • Reaction with blood emits light that can be seen in darkened area

  • Sprayed on area, turn dark, emits blue light


Microcrystalline tests
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
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
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
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


Forensic analysis of semen
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 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