Forensic Serology

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Forensic Serology

• Identification Using Blood Groups

This presentation contains graphic pictures.
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Forensic Serology
Serology term used to describe a broad range of
laboratory tests using reactions of blood serum
and body fluid

• The serology section of a forensic laboratory may
  deal with any or all of the following
• blood typing
• characterization of unknown blood
• stain patterns for crime reconstruction
• paternity testing
• semen identification in rape cases
• DNA techniques used for identification

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The Composition of Blood
Blood is a mixture of many components cells inor
ganic substances (salts) enzymes water proteins
55 of blood content is plasma mostly water
and substances dissolved in it Most of the solid
materials (by weight) are cells red blood cells,
RBCs (erythrocytes) white blood cells
(leukocytes)
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Forensic Characterization of Bloodstains
Three questions that must be answered by the
forensic investigator 1) Is it
blood? Benzidine Test Kastle-Meyer
Test Hemastix (o-tolidine, TMB) Luminol
Test 2) Is it human blood? Precipitin Test 3)
Can it be associated with an individual?
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Luminol

• Red blood cells contain hemoglobin (Hb) the
  protein responsible for transporting oxygen
• Each Hb contains four iron (Fe) containing hemes

Heme structure
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Luminol

• Red blood cells contain hemoglobin (Hb) the
  protein responsible for transporting oxygen
• Each Hb contains four iron (Fe) containing hemes

Heme structure
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Forensic Characterization of Bloodstains
Three questions that must be answers by forensic
investigator 1) Is it blood? Benzidine
Test Kastle-Meyer Test Hemastix (o-tolidine,
TMB) Luminol Test Enzymatic Tests 2) Is it
human blood? Precipitin Test 3) Can it be
associated with an individual?
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Precipitin Test
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Blood Antigens
On the surface of red blood cells are chemical
structures (proteins) called antigens The
presence of antigens allow a living system to
recognize foreign biological substances Antigens
also impart specific characteristics to the red
blood cells. These characteristics can be partly
used to identify individuals Human red blood
cells have more than 15 different antigen types
that have been discovered
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Blood Typing
Blood typing involves determination of the
antigens present on an individuals RBCs The two
most common blood typing systems used are the
A-B-O method and the Rh method type A blood
contain A antigen on RBCs type B blood
contain B antigen on RBCs type AB blood
contains both A and B antigens type O blood
contain no A or B antigens Rh blood contain
Rh antigen Rh- blood no Rh antigen
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Blood Typing
Blood also contains antibodies proteins that
recognize and bind to certain, specific
antigens Blood Type Antigens on
RBC Antibodies A A
anti-B
B B anti-A AB
AB none O
none
both A B
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Blood Typing
When blood containing a specific antigen is mixed
with blood containing the corresponding
antibodies, the blood clots
The clots can then be removed by the host system
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Blood Typing
Human serum containing specific antibodies can be
purchased
Separately mix a drop of unknown blood sample
with drop of each anti-serum
Reaction between blood and anti-serum
No reaction between blood and anti-serum
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Blood Typing Example
A sample of unknown blood is mixed with three
anti-sera samples Tube 1 (Anti-A) No
reaction Tube 2 (Anti B) No reaction Tube 3
(Anti Rh) Cloudy reaction In terms of the
A-B-O and Rh systems, what type blood is the
sample? The ABO antigens are not confined to
RBC 80 of Americans are secretors, found on
other cells
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Blood Typing Example
A sample of unknown blood is mixed with three
anti-sera samples Tube 1 (Anti-A) No
reaction Tube 2 (Anti B) No reaction Tube 3
(Anti Rh) Cloudy reaction In terms of the
A-B-O and Rh systems, what type blood is the
sample? The ABO antigens are not confined to RBC
80 of Americans are secretors, same antigens
found on other cells
O positive
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Blood Splatter Analysis
Categories of Bloodstains Passive
(dripping) Transfer (smearing) Projected
Projected Bloodstains occur in shootings, trauma
from blunt weapons, hacking, or slashing attacks.
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Projected Bloodstain Analysis
Two Important Determinations a. direction of
splatter b. angle of impact with
surface sin ? (width drop / length drop)
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Forensic Characterization of Semen

• Many crimes involve sexual misconduct
• Normal males, upon ejaculation, release seminal
  fluid. This fluid is a mixture of components
• water
• spermatozoa
• enzymes
• inorganic salts
• Semen at a crime scene (clothing, bed sheets,
  carpet, cushions) can be located and identified
  by three common methods
• microscope examination to find sperm
• acid phosphatase test
• p30 (also called prostrate specific antigen)
  immunoassay test

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Forensic Characterization of Saliva
Saliva is a mixture of many components 99
water Mucin (protein helps in swallowing) Amylase
(enzyme to help digest carbohydrates) Cheek cells
(good for DNA) Adults produce 1.0-1.5 liters of
saliva/day and it is not uncommon at crime scenes
(especially involving bite marks).
A simple test for saliva involves mixing starch,
iodine, and a sample of the presumed saliva
together. Starch and iodine are a deep blue color
when mixed together. The amylase breaks down
starch, however, and the color fades (takes about
15 mins _at_ 37 oC).