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Explore the science of serology, the study of antigen-antibody reactions in blood analysis for forensic purposes. From the history of blood typing to modern DNA technology, learn how crucial blood evidence is in solving crimes. Discover the composition of blood, the significance of blood factors, and techniques for analyzing bloodstains to link crimes to suspects or victims.
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Forensic Serology YouTube - The Sam Sheppard case
Introduction • 1901- Karl Landsteiner recognized that human blood was distinguishable by its group or type • Bloodstains are often found at crime scenes (homicides, assaults, rapes, etc.) • Blood Factors (like A-B-O, Rh factor, and others) have been used to link a crime to a suspect or a victim. • Since the early 1990’s, DNA technology has completely changed the way in which bloodstains and other biological evidence is individualized.
The Nature of Blood Blood is composed of : • Plasma- the fluid portion of unclotted blood • Red Blood Cells (erythrocytes) • White blood cells (leukocytes) • Platelets Serum-yellowish liquid that separates from blood when a clot has formed.
Antigens and Antibodies • Antigens-substances, usually proteins, found on the surface of red blood cells that give the cells specific characteristics • Antibodies-proteins found in blood serum that destroy or inactivate a specific antigen by binding to it. • Agglutination-clumping together of red blood cells cause by an antigen/antibody interaction • Serology-the study of antigen-antibody reactions
Blood Typing • Serology – the study of antigen-antibody reactions. Distribution of blood types in the U.S.:
Forensic Characterization of Bloodstains Bloodstains must be analyzed to determine: • Is it blood? • From what species did the blood originate? • How closely can it be associated with a particular individual?
Forensic Characterization of Bloodstains • Color Tests-Kastle-Meyer test-oxidation of hemoglobin in blood produces a deep pink color. • Luminol-reaction with blood produces light; faint blue glow known as luminescence; very sensitive technique • Immunoassays-Antigen-antibody reactions are used to identify blood and also detect drugs in blood
Forensic Characterization of Bloodstains • Microcyrstalline tests-Takayama and Teichmann tests; substances form crystals when they come in contact with hemoglobin; less sensitive than color tests • Precipitin test-used to detect human blood • Gel diffusion-another method for detecting human blood.