Forensic SerologyForensic Serology

YouTube - The Sam Sheppard case

IntroductionIntroduction 1901- Karl Landsteiner recognized that 1901- Karl Landsteiner recognized that

human blood was distinguishable by its human blood was distinguishable by its group or typegroup or type

Bloodstains are often found at crime Bloodstains are often found at crime scenes (homicides, assaults, rapes, etc.)scenes (homicides, assaults, rapes, etc.)

Blood Factors (like A-B-O, Rh factor, and Blood Factors (like A-B-O, Rh factor, and others) have been used to link a crime to a others) have been used to link a crime to a suspect or a victim.suspect or a victim.

Since the early 1990’s, DNA technology Since the early 1990’s, DNA technology has completely changed the way in which has completely changed the way in which bloodstains and other biological evidence bloodstains and other biological evidence is individualized.is individualized.

The Nature of BloodThe Nature of Blood

Blood is composed of :Blood is composed of : Plasma- Plasma- the fluid portion of unclotted the fluid portion of unclotted

blood blood Red Blood Cells (Red Blood Cells (erythrocyteserythrocytes)) White blood cells (White blood cells (leukocytesleukocytes)) PlateletsPlatelets

Serum-Serum-yellowish liquid that separates from yellowish liquid that separates from blood when a clot has formed.blood when a clot has formed.

Antigens and AntibodiesAntigens and Antibodies

Antigens-Antigens-substances, usually proteins, found substances, usually proteins, found on the surface of red blood cells that give the on the surface of red blood cells that give the cells specific characteristicscells specific characteristics

Antibodies-Antibodies-proteins found in blood serum that proteins found in blood serum that destroy or inactivate a specific antigen by destroy or inactivate a specific antigen by binding to it.binding to it.

Agglutination-Agglutination-clumping together of red blood clumping together of red blood cells cause by an antigen/antibody interactioncells cause by an antigen/antibody interaction

Serology-Serology-the study of antigen-antibody the study of antigen-antibody reactionsreactions

Blood TypingBlood Typing

Serology – Serology – the study of antigen-the study of antigen-antibody reactions.antibody reactions.

Distribution of blood types in the U.S.:Distribution of blood types in the U.S.:

O A B AB43% 42 % 12 % 3 %

Blood TypesBlood Types

Blood TypeBlood Type Antigens on Antigens on Red Blood Red Blood CellsCells

Antibodies Antibodies in Serumin Serum

AA AA Anti-BAnti-B

BB BB Anti-AAnti-A

ABAB ABAB Neither anti-A Neither anti-A nor Anti-Bnor Anti-B

OO Neither A nor BNeither A nor B Both anti-A Both anti-A and Anti-Band Anti-B

Forensic Characterization of Forensic Characterization of BloodstainsBloodstains

Bloodstains must be analyzed to Bloodstains must be analyzed to determine:determine:

1.1. Is it blood?Is it blood?

2.2. From what species did the blood From what species did the blood originate?originate?

3.3. How closely can it be associated How closely can it be associated with a particular individual?with a particular individual?

Forensic Characterization of Forensic Characterization of BloodstainsBloodstains

Color Tests-Color Tests-Kastle-Meyer test-Kastle-Meyer test-oxidation of hemoglobin in blood oxidation of hemoglobin in blood produces a deep pink color.produces a deep pink color.

Luminol-reaction with blood produces Luminol-reaction with blood produces light; faint blue glow known as light; faint blue glow known as luminescence; very sensitive luminescence; very sensitive techniquetechnique

Immunoassays-Antigen-antibody Immunoassays-Antigen-antibody reactions are used to identify blood reactions are used to identify blood and also detect drugs in bloodand also detect drugs in blood

Forensic Characterization of Forensic Characterization of BloodstainsBloodstains

Microcyrstalline tests-Microcyrstalline tests-Takayama Takayama and and Teichmann Teichmann tests; substances form tests; substances form crystals when they come in contact crystals when they come in contact with hemoglobin; less sensitive than with hemoglobin; less sensitive than color testscolor tests

Precipitin test-used to detect human Precipitin test-used to detect human bloodblood

Gel diffusion-another method for Gel diffusion-another method for detecting human blood.detecting human blood.