Serology

Serology is the study of blood and other body fluids including sweat,
semen, saliva, and urine.
 A forensic serologist may analyze a variety of
physical evidence with the
intent of finding, identifying and individualizing stains of biological origin.
Blood Characteristics
Blood:
 A complex mixture composed of cells (45%), enzymes, proteins, and
plasma (55%).
 It is composed of three main cells: erythrocytes,
leukocytes, & thrombocytes.
Erythrocytes (RBC):
 The most abundant cells in our blood.
 They are produced in the bone marrow.
 They are responsible for oxygen distribution (contain hemoglobin).
Leukocytes (WBC):
 Part of the immune system & destroys pathogens.
Thrombocytes (Platelets)
 Responsible for blood clotting.
Plamsa:
 Yellowish fluid portion of the blood.
 Principally made of water.
 Contains electrolytes, nutrients and vitamins, hormones, clotting factors,
and proteins such as antibodies.
Blood volume makes up 8% of total body weight.
 Average adult has five liters of blood.
 A 40% (2L) loss of total volume results in irreversible shock (death).
 A 1.5L loss of total volume results in disabling a person.
 There are one billion RBC in 2-3 drops of blood.
 For every 600 RBC, there are about 40 platelets and one WBC.
Blood Terminology
Antigens:
 Responsible for blood type characteristics.
 On the surface of RBC.
 A protein that stimulates the immune system to produce antibodies.
 More than 15 blood antigen systems have been identified.
Antibody:
 A protein that reacts with an antigen.
 Produced by WBC.
 They recognize and bind to certain, specific antigens (agglutination).
Agglutination:
 Clumping of RBC which occurs if blood types with different antigens are
mixed.
ABO System
Karl Landsteiner (1901)
 Discovered the ABO blood system of blood typing.
Leon Lattes (1915)
 Discovered a way of typing dried blood using saline to determine the ABO
system.
Blood type is inherited.
 It can be used to include or exclude a person as a suspect.
 It can not absolutely identify a suspect.
 It can absolutely exclude a suspect.
The groups are based on having an A,B, both or no antigens on RBC.
 There are four different blood types: A,B,AB, and O.
ABO System
Blood
Type
Antigens
on RBC
Antibodies
A
A
Anti-B
B
B
Anti-A
AB
AB
none
O
none
Both Anti-A
& Anti-B
ABO System
Blood
Type
Reaction
w/ Anti-A
Reaction w/
Anti-B
A
Agglutination
No
Agglutination
B
No
Agglutination
Agglutination
AB
Agglutination
Agglutination
O
No
Agglutination
No
Agglutination
Distribution of blood types:
ABO System
Distribution of blood types:
Blood Type
Percentage of
Population
A
40%
B
11%
AB
4%
O
45%
ABO System
Rh Factor (+ or -)
 Rh stands for rhesus factor, first identified in rhesus monkeys in 1940.
 Rh is antigen D on the surface of RBC.
 It is inherited separately from the A & B antigens.
 Presence of antigen D, Rh positive.
 Absence of antigen D, Rh negative.
 85% of Caucasians, 94% of African Americans, and 99% of all Asians are
Rh positive.
Blood Donation
 AB is the universal recipient.
 O is the universal donor.
 If you are Rh +, you can accept + or – .
 If you are Rh -, you can only accept -.
Analysis of Blood
 Three questions must be answered by the forensic serologist:
1. Is it blood?
2. Is it human blood?
3. Can it be associated with
an individual?
Analysis of Blood
Is it Blood? (Presumptive Tests)
 Kastle-Meyer Color Test:
-Phenolphthalein, hydrogen
peroxide, and suspected blood
stain are mixed; positive
reaction indicated by a deep
pink color.
-It reacts with iron in
hemoglobin to produce a pink
color.
Is it Blood? (Presumptive Tests)
 Kastle-Meyer Color Test:
-Results are not definite.
-Substances other than blood
may produce the color
change (potatoes and
horseradish).
Is it Blood? (Presumptive Tests)
 Hemastix Test:
-Used in the field by
investigators.
-A dipstick moistened with
distilled water is placed in
contact with the suspect
blood.
Is it Blood? (Presumptive Tests)
 Hemastix Test:
- It reacts with iron in
hemoglobin causing a green
color change.
Is it Blood? (Presumptive Tests)
 Luminol Test:
-A test for blood that
produces light
(luminescence) when it
reacts with blood.
Is it Blood? (Presumptive Tests)
 Luminol Test:
-Extremely sensitive-it is
capable of detecting blood
stains that have been diluted
up to 300,000 times.
Is it Blood? (Presumptive Tests)
 Luminol Test:
-Limitations:
1. Reacts with copper
containing alloys, certain
bleaches and citrus fruits.
2. Residual bleach will cause
the entire scene to glow.
Analysis of Blood
Is it Blood? (Presumptive Tests)
 Luminol Test:
-Limitations:
3. Its presence prevents
other tests from being
performed. (DNA analysis
can still be performed).
Analysis of Blood
Is it Blood? (Presumptive Tests)
 Leucomalachite Test:
-A mixture of acetic acid,
distilled water, leucomalachite
green, and sodium perborate
will turn a sample green in the
presence of blood.
Analysis of Blood
Is it Animal or Human?
 Precipitin Test:
-Based on the theory of
antigen-antibody reactions.
-An animal (rabbit) is injected with
human blood.
-The animal creates antibodies that
can be recovered and used to test
for various human blood antigens.
Analysis of Blood
Is it Animal or Human?
 Precipitin Test:
-The recovered antibodies
are called human
antiserum.
 Precipitin Test:
-To test for human blood,
human antiserum and an
unknown blood are put
together—if the blood is
human a precipitate will form.
Analysis of Blood
Is it Animal or Human?
 Differences:
-Platelets and leukocytes do
not differ significantly.
-Mature human RBC lack a
nucleus.
Analysis of Blood
Can it be Individualized?
 DNA Analysis:
-Characterizes bloodstains to a
particular individual using blood
factors.
Blood Spatter Interpretation
 It applies principles from biology, chemistry, physics, and math to
interpret bloodstain patterns within a forensic setting.
 It is used to determine what
happened at a crime scene &
the sequence of events that
took place.
 It can determine:
-Location and description of
individual stains and
patterns
-Mechanism that created
the stains
-Direction blood droplet was
traveling
Blood Spatter Interpretation
-Origin of bloodstain
-Position of victim &
assailant
-Distance of bloodstain from
target
-Speed with which blood
left its source
-Minimum number of blows
Blood Spatter Interpretation
 Blood drop characteristics:
-A free falling drop of
blood forms a sphere or
ball.
-The spherical drop will
break when it strikes
another object or when
acted upon by some force.
Blood Spatter Interpretation
-Blood droplet volume is
directly dependent upon the
surface or orifice from
which it originates.
-The impact area it strikes
is called the target.
Blood Spatter Interpretation
-The higher the height and
the faster a drop falls the
larger its diameter.
-Texture of surface changes
the shape of drop.
Blood Spatter Interpretation
 Spatter size is dependent
upon velocity :
-Low Velocity
-Results from the pull of
gravity.
- Spatter is 5 ft/s & usually
3 mm or greater in diameter .
-Indication of dripping blood
Blood Spatter Interpretation
-Medium Velocity
-Results from an object as a
fist or blunt object.
-Spatter is 5 – 25 ft/s with a
<3 mm diameter.
Blood Spatter Interpretation
-High Velocity
-Results from gunshots, power
tools, an object striking with
extreme velocity, or an
explosion.
-Spatter is 100+ ft/s with a
diameter of < 1 mm.
-May be referred to as fly
specks
Blood Spatter Interpretation
 Angle of Impact:
-Angle at which blood strikes a
target surface.
-A droplet will remain spherical
if it falls at a 90° angle.
-Droplets elongate as the
angle decreases from 90°
to 0°
Blood Spatter Interpretation
-The more acute the angle of
impact, the more elongated
the stain.
- At about 30° the
stain will begin to produce
a tail.
Blood Spatter Interpretation
Blood Spatter Interpretation
The shape of a blood drop can
be determined by the formula:
Blood Spatter Interpretation
Blood Spatter Interpretation
Tail points
in direction
of travel.
 The Point of Convergence:
-The intersection of two bloodstain paths, where the stains come from
opposite sides of the impact pattern.
Blood Spatter Interpretation
 The Area of Convergence:
-The point of origin; the spot
where the “blow” occurred.
-Formed by the intersection of
several stains from opposite
sides of the impact pattern.
Categories of Blood Stains
Categories of Blood Stains
Passive: Created when the force
acting on the blood is gravity.
Categories of Blood Stains
Projected: Occur when some form
of energy has been transferred to
a blood source.
Categories of Blood Stains
Transfer or contact: Produced
when an object with blood on it
comes into contact with an object
or a surface that does not have
blood on it.
Categories of Blood Stains
Swipe: Created when
wet blood is transferred to a
surface which did not have
blood on it.
Categories of Blood Stains
Wipe: Created when a nonblood bearing object moves
through a wet bloodstain,
altering the appearance of the
original stain.
Categories of Blood Stains
Cast off: Created when blood
is thrown from an object in
motion.
Categories of Blood Stains
Arterial Spurting: Resulting from
blood exiting the body under
pressure from a breached artery.
Secretors
 80% of individuals are classified
as secretors.
 This means that their blood
type antigens are found in high concentrations in most body fluids (salvia,
semen,
gastric juices).
 Semen and salvia have a higher
concentration of antigens than
blood.
 Semen can be detected by two
methods:
-UV Light
-Acid Phosphatase Color Test
 UV Light
-Semen will fluoresce under UV
light when it comes in contact
with 4-methyl umbelliferyl
phosphate (MUP).
Secretors
 Acid Phosphatase Color Test
- Acid phosphate is an enzyme
secreted by the prostate
gland into seminal fluid that
is in far greater
concentrations than those
found in any other body
fluids.
-Its presence can be detected
by placing sodium alpha
naphthylphosphate and
Fast Blue B solution are
on it.
-Large areas or fabrics can be
quickly searched by moistening
filter paper with the detector
solutions and rubbing over the
suspect area.
Secretors
Secretors
Secretors
-Some substances will give a
false-positive result (fruit
juices), but none of these
substances will react with
the speed of seminal fluid.
-It turns a purple color if it
is present.
-If a false-positive results
occur then p-30 or prostate
specific antigen (PSA) is used
to detect seminal plasma.
Secretors
Secretors
-Formation of a visible line
between the wells of anti p-30
and semen extract–proves the
stain is seminal.
People of Historical Significance
Paul Kirk (1902-1970) was a professor of criminalistics and biochemistry at
Berkeley in California. He actively assisted law enforcement organizations
from 1935 to 1967. His book, Crime Investigations, contained a chapter in
which he discussed the application of blood stain pattern analysis to
criminal investigations. Dr. Kirk analyzed the blood stain pattern photos
from the Sam Sheppard case and was instrumental in Sheppard’s release
at his second trial.