Blood
Blood
Objectives
You will understand:
That an antibody and an antigen of
different types will agglutinate, or
clump, when mixed together.
That the significance of the evidence
depends on a characteristic’s
relative occurrence in the
population.
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Blood
Objectives, continued
You will be able to:
Determine whether a stain is blood.
Determine whether a bloodstain is
human or animal blood.
Determine the blood type of a
simulated bloodstain using the
ABO/Rh system.
Explore bloodstain patterns as a
function of velocity, direction, and
height of fall.
Use technology and mathematics to
improve investigations and
communications.
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Blood
Serology
Serology is the examination and analysis of body
fluids. A forensic serologist may analyze a variety of
body fluids including saliva, semen, urine, and
blood.
From 1950 to the late 1980s, forensic serology was a
most important part of lab procedures. With the
development of DNA techniques, more time, money,
and significance were placed on developing DNA
labs. However, with limited funds and the time
required for DNA testing, most labs still use many of
the basic serology testing procedures.
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Blood
Blood Characteristics
Plasma is the fluid portion of the blood (55
percent).
Cells (45 percent)
Erythrocytes are red blood cells. They
are responsible for oxygen
distribution.
Leukocytes are the white blood cells;
they are responsible for “cleaning”
the system of foreign invaders.
Thrombocytes or platelets are
responsible for blood clotting.
Serum is the liquid that separates from the
blood when a clot is formed.
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Blood
Historical Perspective of Blood Typing
Around 1900, Karl Landsteiner discovered that there are four
different types of human blood based on the presence or
absence of specific antigens found on the surface of the red
blood cells.
In 1940, Landsteiner and Weiner reported the discovery of the Rh
factor by studying the blood of the Rhesus monkey. 85 percent
of Caucasians, 94 percent of Black Americans, and 99 percent
of all Asians are Rh positive.
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Blood
Blood Terminology
ABO blood groups—based on having A, B, both, or no antigens on
red blood cells. Around 1900, Karl Landsteiner discovered that there
are four different types of human blood based on the presence or
absence of specific antigens found on the surface of the red blood
cells.
Rh factor—may be present on red blood cells; positive if present and
negative if not. In 1940, Landsteiner and Weiner reported the
discovery of the Rh factor by studying the blood of the Rhesus
monkey. 85 percent of Caucasians, 94 percent of Black Americans,
and 99 percent of all Asians are Rh positive.
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Blood
Antigen—a substance that can stimulate the body
to make antibodies. Certain antigens (proteins)
found in the plasma of the red blood cell’s
membrane account for blood type. (0-4:17 only of the
10:45 min video.
Antibody—a substance that reacts with an
antigen
Agglutination—clumping of red blood cells; will
result if blood types with different antigens are
mixed. ~ 2:00 min
http://nobelprize.org/educational/medicine/landsteiner/readmore.html
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Blood
Unknown Stain at a Scene
Questions to be answered:
Is it blood?
Is it human blood?
Whose is it?
Determine blood type, alcohol content,
drugs present
Determine the method(s) in which
blood may have been deposited
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Blood
Presumptive Tests for Blood Determination
Kastle-Meyer color test—a mixture of phenolphthalein and hydrogen
peroxide; the hemoglobin will cause the formation of a deep pink
color if blood is present
Hematest tablet—reacts with the heme group in blood, causing a bluegreen color
Luminol test—reaction with blood to produce light
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Blood
Human versus Animal Blood
Microscopic observation-Animals have larger nucleic
red blood cells
Precipitin test—blood is injected into a rabbit;
antibodies are formed; the rabbit’s blood is
extracted as an antiserum; the antiserum is placed
on sample blood. The sample will react with human
proteins if human blood is present. This test is very
sensitive and requires only a small amount of blood.
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Blood
Animal Blood
 Larger nucleic red blood
cells
 Frog blood
Smaller nucleic red blood cells 
Human Blood 
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Blood
Microscopic
Views
Fish Blood
Bird Blood
Horse Blood
Frog Blood
Cat Blood
Dog Blood
Human Blood
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Snake Blood
Blood
Human Blood
Red blood cells are most
numerous; 5 to 6 million per
mm3
White blood cells are larger and
less numerous; 5,000 to
10,000 per mm3
Platelets are tiny, cellular
fragments; 350,000 to
500,000 per mm3
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Blood
Blood Typing
Blood type A has antigen A on the surface of the cell and will
agglutinate with blood type B.
Blood type B has antigen B on the surface of the cell and will
agglutinate with blood type A.
Blood type AB has antigens A and B on the surface of the cells and
will not agglutinate with either type A or type B blood.
Blood type O has neither antigen A nor B and will not agglutinate.
Secretors
Eighty percent 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.
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Blood
Blood Groups
Type
Antigen
Antibody
Can Give Can Get
Blood To Blood From
A
A
B
A, AB
O, A
B
B
A
B, AB
O, B
AB
A and B
Neither
A nor B
AB
A, B, O, AB
O
Neither
A nor B
A and B
A, B, O, AB
O
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Blood
Population Distribution of Blood Types in the
U.S.
Type
Percent
O
45
A
40
B
11
AB
4
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Blood
How common is your blood type?
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Blood
Blood Transfusions
A blood transfusion is a procedure in which blood is given to a patient through an
intravenous (IV) line in one of the blood vessels. Blood transfusions are done to
replace blood lost during surgery or a serious injury. A transfusion also may be
done if a person’s body can't make blood properly because of an illness.
Who can give you blood?
People with TYPE O blood are called
Universal Donors, because they can give
blood to any blood type.
Universal
Donor
People with TYPE AB blood are called
Universal Recipients, because they can
receive any blood type.
Rh +  Can receive + or Rh -  Can only receive -
Universal
Recipient
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Blood
Blood Products from Blood Banks,
Donations and Drives
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Blood
Blood Evidence
Class evidence for blood includes blood
type.
If you can determine the DNA, you will have
individual evidence.
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Blood
Blood Pattern Reconstruction
Scene Pattern
Reconstruction
Lab Results
Reconstruction
1. Stain condition
1. Genetic marker typing
2. Pattern
2. Age determination
3. Distribution
3. Source determination
4. Location
4. Race determination
5. Directionality
5. Sex determination
—From Cracking Cases by Dr. Henry C. Lee and
Thomas W. O’Neil
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Blood
Blood Spatter Evidence
A field of forensic investigation that deals with the physical
properties of blood and the patterns produced under different
conditions as a result of various forces being applied to the
blood. Blood, as a fluid, follows the laws of physics.
Bloodstain patterns are considered circumstantial evidence in a
courtroom. Experts can argue many points, including direction
of travel, height of the perpetrator, position of the victim,
left/right hand, whether the body was moved, etc.
23
Blood
People of Historical Significance
Paul Kirk (1902–1970) was a professor of criminalistics
and biochemistry at the University of California at
Berkeley. He actively assisted law enforcement
organizations from 1935 to 1967. His book Crime
Investigation contained a chapter in which he
discussed the application of bloodstain pattern
analysis to criminal investigations.
Dr. Kirk analyzed the bloodstain pattern photos from the
Sam Sheppard case and was instrumental in
Sheppard’s release after his second trial. Find out
more about the case at truTV’s Crime Library.
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Blood
Blood Droplet Characteristics
A blood droplet remains spherical in space until it collides with a
surface.
Once a blood droplet impacts a surface, a bloodstain is formed.
Droplets falling from the same height, hitting the same surface at
the same angle, will produce stains with the same basic shape.
How will the shape change as the height is increased or decreased?
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Blood
Blood Droplet Volume
A droplet contains approximately 0.05 cc of fluid.
Is not the same for all blood droplets, but is generally from 0.03 cc to
0.15 cc
Is directly dependent upon the surface or orifice from which it
originates
The impact area is called the target.
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Blood
Conditions Affecting Shape of Blood Droplet
Size of the droplet
Angle of impact
Velocity at which the blood droplet left its origin
Height
Texture of the target surface
• On clean glass or plastic—droplet will have smooth outside edges
• On a rough surface—will produce scalloping on the edges
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Blood
Conditions Affecting Shape of Blood Droplet
Size of the droplet
Angle of impact
Velocity at which the blood droplet left its origin
Height
Texture of the target surface
• On clean glass or plastic—droplet will have smooth outside edges
• On a rough surface—will produce scalloping on the edges
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Blood
Angle of Impact
29
Blood
Questions Answered by Blood
Spatter Interpretation
The distance between the target surface and the origin of the
blood
The point(s) of origin of the blood
Movement and direction of a person or an object
The number of blows, shots, etc., causing the bloodshed and/or
the dispersal of blood
Type and direction of impact that produced the bloodshed
The position of the victim and/or object during bloodshed
Movement of the victim and/or object after bloodshed
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Blood
Bloodstain Patterns
Considerations
The harder and less porous the surface, the
less the blood drop will break apart.
The softer and more porous the surface, the
more the blood drop will break apart.
The pointed end of the bloodstain faces the
direction of travel.
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Blood
Bloodstain Terminology
Angle of impact—angle at which blood strikes a target surface
Bloodstain transfer—when a bloody object comes into contact with a
surface and leaves a patterned blood image on the surface
Backspatter—blood that is directed back toward the source of
energy
Cast-off—blood that is thrown from an object in motion
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Blood
Bloodstain Terminology, continued
Contact stain—bloodstains caused by contact between a wet bloodbearing surface and a second surface that may or may not have blood
on it
• Transfer—an image is recognizable and may be identifiable
with a particular object
• Swipe—wet blood is transferred to a surface that did not
have blood on it
• Wipe—a non-blood-bearing object moves through a wet
bloodstain, altering the appearance of the original stain
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Blood
Bloodstain Terminology, continued
Directionality—relates to the direction a drop of blood travels in
space from its point of origin
Terminal velocity—the greatest speed to which a free-falling drop of
blood can accelerate in air. It is dependent upon the acceleration of
gravity and the friction of the air against the blood—approximately
25.1 feet/second.
• High velocity—greater than 25 feet per second, usually
100 feet per second; gives a fine mist appearance.
• Medium velocity—5 to 25 feet per second.
• Low velocity—5 feet per second or less
High, Medium, and Low described in detail on the next three slides.
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Blood
High velocity—greater than 25 feet per
second, usually 100 feet per second; gives
a fine mist appearance. result of gunshot
wounds explosions. The pattern appears
as a spray of minute drops. Bullet wounds
leave both front and back sprays. Back
sprays are usually smaller than front
sprays.
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Blood
Medium velocity—5 to 25 feet per second.
the result of being hit with blunt objects,
stab wounds, or being dealt particularly
vicious blows with fists. In cases where the
victim has been beaten or stabbed, the
arteries can be damaged. If the wounds
are close enough to the skin, the victim will
bleed faster and blood may spurt out of
the wound as the heart beats. The
outcome is a large amount of blood and a
distinctive pattern called arterial spurting
pattern. The diameter of the droplets is
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Blood
 Low velocity—5 feet per second or less.
low velocity spatter is typically caused by
dripping blood. This type of spatter is
usually the result of a sustained injury
rather than by the impact that caused the
wound. Blood pooling around a body and
transfers are also considered low velocity
spatters. Low velocity spatter can also be
caused by punches or kicks
37
Blood
Blood Spatter Analysis
There are also multiple ways to analyze blood
spatter.
One method is to use a trigonometric calculation.
The measurements of the blood stain will
become the sides of a right triangle. The length
is the hypotenuse and the width is the opposite
angle. The analyst has to measure the spatter’s
length and width and then insert it into the
equation on the next slide.
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Blood
Bloodstain Patterns
The shape of a blood drop:
Round—if it falls straight down at a 90-degree angle
Elliptical—blood droplets elongate as the angle decreases from 90
to 0 degrees; the angle can be determined by the following
formula:
Impact angle, i = arc sin ( drop width, w )
( drop length, l )
The arc sin can be calculated with your calculator or found by
using a table such as Table 11.6 on page 327
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Blood
Impact
The more acute the angle of
impact, the more elongated the
stain.
90-degree angles are perfectly
round drops; 80-degree angles
take on a more elliptical shape.
At about 30 degrees the stain will
begin to produce a tail.
The more acute the angle, the easier it is to determine the
direction of travel.
40
Blood
Bloodstain Patterns
The harder and less porous the
surface, the less the blood drop
will break apart.
The softer and more porous the
surface, the more the blood
drop will break apart.
The pointed end of the bloodstain
faces the direction of travel.
41
Blood
Area of Intersection and Convergence
The location of the blood source can
be determined by drawing lines
from the various blood droplets to
the point where they intersect.
The area of convergence is the point
of origin—the spot where the
“blow” occurred. It may be
established at the scene by
measurement of angles with the
use of strings.
42
Blood
Area of Intersection and Convergence
 Another method of finding the area of
convergence is called stringing. The
analyst documents the location of the
spatters on a coordinate system and
the sets up a level line to show the
spatters in relation to the floor and
ceiling. Using elastic string, they
draw lines from each spatter through
the level line. Then using a protractor
on the level line, the analyst
determines the angle of flight to try
and find the area of convergence.
43
Blood
44
Blood
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 points, including direction of
travel, height of the perpetrator, position of the victim, left/right
hand, whether the body was moved, etc.
45
Blood
Secretors
Eighty percent of the population are secretors. Their bloodtype antigens are found in high concentration in their
body fluids such as saliva, semen, vaginal secretions,
and gastric juices.
46
Blood
People in the News
Herbert L. MacDonell is considered by many to be the father of
modern bloodstain pattern analysis. He is the director of the Lab
of Forensic Science and founder of the Bloodstain Evidence
Institute (1973) in Corning, NY. His book Bloodstain Pattern
Interpretation helped to jump-start this discipline. He has
consulted on criminal cases in all 50 states, in addition to
testifying in the O. J. Simpson trial and in the assassination cases
of Sen. Robert F. Kennedy and
Dr. Martin Luther King, Jr.
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Blood
More about Serology
For additional information about blood evidence, and famous
crimes that involve serology, check out truTV’s Crime Library at:
www.crimelibrary.com/criminal_mind/forensics/serology/1.html
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