1. Chapter 10 3/30/12
Chapter 11 Notes!
Serology!
Blood Evidence!
Serology is the examination
and analysis of body fluids.
 Analyzes body fluids including saliva,
semen, urine, and blood
 Until the use of DNA, serology was
one of the most important forensic
tools
Blood : The Basics! History of Blood Typing!
2 parts of blood: Karl Landsteiner (circa 1900)
 Discovered 4 different types of human
 Plasma(fluid = blood
55%).  based on the presence or absence of
specific antigens found on the surface of
 Cells (45%) the red blood cells.
Erythrocytes - Landsteiner and Weiner (1940)
red blood cells.  Discovered the Rh factor by studying the
Serum is the liquid Leukocytes - blood of the Rhesus monkey
that separates from white blood  85% of Caucasians, 94%of Black
Americans, and 99%of all Asians are Rh
the blood when a cells positive.
clot is formed.
Thrombocytes -
Important Terms! Important Terms!
Antigen—a substance that
can stimulate the body to ABO blood groups—
make antibodies. Certain based on having A, B,
antigens (proteins) found in both, or no antigens
the plasma of the red blood on red blood cells
cell’s membrane account for Rh factor—may be
blood type. present on red blood
Antibody—a substance that cells; positive if
reacts with an antigen present and negative
if not
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2. Chapter 10 3/30/12
Important Terms! Unknown Stain at a Scene!
Agglutination—clumping of red
Questions to
blood cells; will result if blood types be answered:
with different antigens are  Is it blood?
 Is it human blood?
 Whose is it?
 Determine blood type,
alcohol content, drugs
present Some stains
obvious, others
I googled “blood type  Determine the method(s) in could be something
agglutination” and this was else, like red wine
the 1st picture! WTF??!?!!
which blood may have been
deposited
Blood Determination! Latent Blood Determination!
Presumptive test: used to initially confirm a
stain is blood. Can be a false positive; need a
confirmation test Luminol test
Kastle-Meyer color test—a
reaction with blood to
mixture of phenolphthalein and produce light
hydrogen peroxide; the • Glows in contact with blood
hemoglobin will cause the
formation of a deep pink color if • Sometimes UV helps to
blood is present visualize
Hematest tablet—reacts with the • Many false positives,
heme group in blood, causing a including bleach
blue-green color
Human vs. Animal Blood! Human Blood Typing!
Blood Groups
2 main ways to tell if blood is human: Type Antigen Antibody Can Give Can Get
Blood To Blood From
 Microscopic observation
A A B A, AB O, A
 Precipitin test
• Animal serum with human antibodies is Animal
used B B A B, AB O, B
Human
• Combine animal serum with unknown
blood sample Neither A
AB A and B nor B
AB A, B, O, AB
• Antiserum will react with human
proteins. This test is very sensitive and
requires only a small amount of blood. O Neither A A and B A, B, O, AB O
nor B
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3. Chapter 10 3/30/12
Blood Types in US! Blood Pattern Reconstruction!
Blood Type Frequency
in US Population
Scene Pattern Lab Results
O+
37.4%
Reconstruction Reconstruction
A+
35.7%
1. Stain condition 1. Genetic marker typing
B+
8.5%
2. Pattern 2. Age determination
O-
6.6%
3. Distribution 3. Source determination
A-
6.3%
4. Location 4. Race determination
AB+
3.4%
B-
1.5%
5. Directionality 5. Sex determination
AB-
.6%
Blood Spatter! Blood Droplet Characteristics!
Blood Spatter Analysis: A field of forensic A blood droplet remains spherical
investigation that deals with the physical properties in space until it collides with a
of blood and the patterns produced under different surface.
conditions as a result of various forces being Once a blood droplet impacts a
surface, a bloodstain is formed.
applied to the blood. Blood, as a fluid, follows the
laws of PHYSICS. Droplets falling from the same
Dear God, did height, hitting the same surface at
she just say
PHYSICS!!?!?!
the same angle, will produce
stains with the same basic shape.
Blood Droplet Volume! Conditions Affecting Shape of Blood Droplet!
A droplet contains approximately 0.05 cc of 1. Size of the droplet
fluid.
2. Angle of impact
Is not the same for all blood droplets, but is
generally from 0.03 cc to 0.15 cc 3. Height
4. Velocity at which the blood droplet left its origin
Is directly dependent upon the surface or
orifice from which it originates 5. Texture of the target surface
• On clean glass or plastic—droplet will have smooth
The impact area is called the target. outside edges
• On a rough surface—will produce scalloping on the
edges
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4. Chapter 10 3/30/12
What Spatter Analysis Can Show! Bloodstain Terminology!
 The distance between the target surface and the Angle of impact—angle at which
origin of the blood
blood strikes a target surface
 The point(s) of origin of the blood
 Movement and direction of a person or an object Bloodstain transfer—when a
 The number of blows, shots, etc., causing the bloody object comes into contact
bloodshed and/or the dispersal of blood with a surface and leaves a
 Type and direction of impact that produced the patterned blood image on the
bloodshed
surface
 The position of the victim and/or object during
bloodshed Cast-off—blood that is thrown from
 Movement of the victim and/or object after an object in motion
bloodshed
Bloodstain Terminology! Bloodstain Terminology!
Backspatter Contact stain—bloodstains caused by
contact between a wet blood-
blood that is
bearing surface and a second
directed back surface that may or may not have
toward the source of blood on it
energy Swipe—wet blood is transferred to a
surface that did not have blood on it
Forward spatter
blood that is Wipe—a non-blood-bearing object
moves through a wet bloodstain,
directed away from altering the appearance of the original
the source of energy stain
Bloodstain Terminology! Bloodstain Terminology!
Directionality—relates to the High velocity—greater than 25
direction a drop of blood travels in feet per second, usually 100 feet
per second; gives a fine mist
space from its point of origin appearance (gun)
Terminal velocity—the greatest
speed to which a free-falling drop of Medium velocity—5 to 25 feet
blood can accelerate in air. It is per second (blunt force/stabbing)
dependent upon the acceleration of
gravity and the friction of the air
Low velocity—5 feet per second
against the blood—approximately or less (blood dripping)
25.1 feet/second.
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5. Chapter 10 3/30/12
Bloodstains Patterns! Bloodstains Patterns!
Impact
The shape of a blood drop:  The more acute the angle
of impact, the more
Round—if it falls straight down at a 90-degree elongated the stain.
angle
 90-degree angles are
Elliptical—blood droplets elongate as the angle perfectly round drops; 80-
decreases from 90 to 0 degrees degree angles take on a
more elliptical shape.
 At about 30 degrees the
Impact angle = sin-1 (arcsin) width stain will begin to produce
length a tail. The more acute the angle, the
easier it is to determine the
direction of travel.
Bloodstains Patterns! Where did the blood come from?!
Area of Intersection and Convergence
 The harder and less porous The location of the blood source
the surface, the less the can be determined by drawing
blood drop will break apart. lines from the various blood
droplets to the point where they
 The softer and more porous intersect.
the surface, the more the The area of convergence is the
blood drop will break apart. point of origin; the spot where the
“blow” occurred. It may be
 The pointed end of the
established at the scene by
bloodstain faces the measurement of angles with the
direction of travel. use of strings.
Using cool strings or lasers! Blood Evidence!
Class evidence for blood
includes blood type. If you
can determine the DNA, you
will have individual evidence.
Bloodstain patterns are considered
circumstantial evidence in a
courtroom. Experts can argue many
Colored strings attached to the wall This is actually the use of lasers
to reconstruct bullet trajectories,
points, including direction of travel,
above this bed at each blood drop
but the idea is the same with height of the perpetrator, position of
helps to determine the position of the
victim on the bed. blood spatter. the victim, left/right hand, whether the
body was moved, etc.
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6. Chapter 10 3/30/12
Secretors!
 80% of the population are
secretors. Their blood-type
antigens are found in high
concentration in their body fluids
such as saliva, semen, vaginal
secretions, and gastric juices.
 Allows for blood typing when no
blood is present – gives more
class evidence.
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