Download Is it blood?

CHAPTER 11 – BLOOD FORENSICS
Serology
1. ________________ is the examination and analysis of body fluids.
2. A forensic serologist may analyze a variety of body fluids including
saliva, semen, urine, and blood.
3. 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.
Blood Characteristics
1. Plasma
– ____________________________________________________
– ________of total volume of blood
– ________water
– ________salts, proteins, glucose, amino acids, enzymes,
hormones, and cellular wastes
2. Cells (45 percent)
– Erythrocytes ________:
• Responsible for ____________________________
• _________________________
– Leukocytes _________:
• responsible for __________ the system of foreign invaders.
• _________________________
– Thrombocytes __________:
• responsible for ______________________.
3. Serum is the liquid that separates from the blood when a clot is
formed.
Historical Perspective of Blood Typing
1. Around 1900, Karl Landsteiner discovered that there are ____different
types of human blood based on the presence or absence of specific
_____________ found on the surface of the __________________.
2. 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.
Blood Terminology
1. ABO blood groups—based on having A, B, both, or no antigens on
red blood cells
2. Rh factor—may be present on red blood cells; ___________ if present
and ____________ if not
3. 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.
4. Antibody—_____________________________________________
5. Agglutination—_______________________________; will result if
blood types with different antigens are mixed
Unknown Stain at a Scene
Questions to be answered:
1. Is it blood?
2. Is it human blood?
3. Whose is it?
– Determine blood type, alcohol content, drugs present
– Determine the method(s) in which blood may have been
deposited
Presumptive Tests for Blood Determination
1. Kastle-Meyer color test—
– a mixture of _________________ and ____________________
– the hemoglobin will cause the formation of a _________________
____________________________________________________
2. Hematest tablet—reacts with the heme group in blood, causing a
________________________
3. Luminol test
– Chemical that reveals ___________________________
– Glows __________ in the dark
– Capable of detecting bloodstains diluted up to 300,000 times
– ____________________________________________________
– ____________________________________________________
– Reaction with blood to produce light
– The hydrogen peroxide and the luminol are actually the principle
players in the chemical reaction, but in order to produce a strong
glow, they need a catalyst to accelerate the process.
– The mixture is actually detecting the presence of such a catalyst,
in this case the ______________________________________
Human versus Animal Blood
1. Microscopic observation
2. Precipitin test—
– blood is injected into a ___________________
– ___________________ are formed
– the rabbit’s blood is extracted as an _______________
– 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.
3. Animal Blood - Larger nucleic red blood cells
4. Human Blood
– Red blood cells are most numerous; ______________________
– White blood cells are larger and less numerous; ____________
_____________________________
– Platelets are tiny, cellular fragments; ______________________
Blood Typing
1. Blood type A
– _______________ on the surface of the cell and
– will agglutinate with blood type _____.
2. Blood type B
– _______________ on the surface of the cell
– will agglutinate with blood type _____.
3. Blood type AB
– _________________________ on the surface of the cells
– will not agglutinate with either type A or type B blood.
4. Blood type O
– ______________________________________________
– will not agglutinate.
Blood Groups
Type
A
B
AB
O
Antigen
Antibody
Can give blood to? Can get blood from?
Population Distribution of Blood Types in the U.S.
Type
O
A
B
AB
Percent
Blood Pattern Reconstruction
Scene Pattern Reconstruction
1.
2.
3.
4.
5.
Lab Results Reconstruction
6.
7.
8.
9.
10.
Sex determination
Blood Spatter Evidence
1. A field of forensic investigation that deals with the physical properties
of blood and the patterns produced under different conditions as a
result of ____________________ being applied to _____________
2. Blood, as a fluid, follows the laws of physics.
People of Historical Significance
Paul Kirk (1902–1970)
1. was a professor of criminalistics and biochemistry at the University of
California at Berkeley.
2. He actively assisted law enforcement organizations from 1935 to 1967.
3. His book _______________________contained a chapter in which he
discussed the application of bloodstain pattern analysis to criminal
investigations.
4. Dr. Kirk analyzed the bloodstain pattern photos from the ___________
_________________ case and was instrumental in _______________
release after his second trial. Find out more about the case at truTV’s
Crime Library.
Blood Droplet Characteristics
1. A blood droplet ____________________________________________
________________________________________________________
2. Once a blood droplet impacts a surface, a ______________________
3. Droplets falling from the _____________, hitting the _____________
at the _____________, will produce stains with the same basic shape.
4. How will the shape change as the height is increased or decreased?
Blood Droplet Volume
1. A droplet contains approximately __________of fluid.
2. Is not the same for all blood droplets, but is generally from 0.03 cc to
0.15 cc
3. Is directly dependent upon ___________________________________
________________________________________________________
4. The impact area is called the _______________.
Conditions Affecting Shape of Blood Droplet
1. ________________________________________________________
2. ________________________________________________________
3. ________________ at which the blood droplet left its origin
4. ________________________________________________________
5. Texture of the target surface
– On clean glass or plastic—droplet will have _________________
– On a rough surface—will produce _________________________
Questions Answered by Blood Spatter Interpretation
1. The distance between the target surface and the origin of the blood
2. The point(s) of origin of the blood
3. Position of the perpetrator relative to the victim
4. Origin of the blood
5. Sequence of events
6. Type of weapon used
7. Movement and direction of a person or an object
8. The number of blows, shots, etc., causing the bloodshed and/or the
dispersal of blood
9. Type and direction of impact that produced the bloodshed
10.
The position of the victim and/or object during bloodshed
11.
Movement of the victim and/or object after bloodshed
Bloodstain Terminology
1. __________________—angle at which blood strikes a target surface
2. ____________________—when a bloody object comes into contact
with a surface and leaves a patterned blood image on the surface
3. Backspatter—____________________________________________
4. Cast-off—________________________________________________
5. _____________________—bloodstains caused by contact between a
wet blood-bearing surface and a second surface that may or may not
have blood on it
– _____________________—an image is recognizable and may be
identifiable with a particular object
– ________________—wet blood is transferred to a surface that
did not have blood on it
– ________________—a non-blood-bearing object moves through
a wet bloodstain, altering the appearance of the original stain
6. Directionality
– Relates to the direction a drop of blood travels in space from its
point of origin
– ____________________________________________________
7. Terminal velocity
– the ______________________ to which a free-falling drop of
blood can accelerate in air.
– dependent upon the acceleration of gravity and the friction of the
air against the blood—approximately __________________
High Velocity Blood Spatter
1. greater than ___________________, usually100 feet per second;
2. ____________________________________________________
3. Collection of small blood drops.
4. ____________________________________________________
Medium Velocity Blood Spatter
1. 5-25 ft/s (1.5-7.5 m/s)
2. ____________________________________________________
3. ____________________________________________________
Low Velocity Blood Spatter
1. 5 ft/s or less (less than 1.5 m/s)
2. ____________________________________________________
3. Drops larger than 3mm in diameter
Bloodstain Patterns
The shape of a blood drop:
1. _____________—if it falls straight down at a 90-degree angle
2. _________________—blood droplets elongate as the angle
decreases from 90 to 0 degrees
Impact
1. ________________________________________________________
2. 90-degree angles are perfectly ____________ drops; 80-degree
angles take on a more elliptical shape.
3. At about ______________ the stain will begin to produce a ________
4. The more acute the angle, the easier it is to determine the direction of
travel.
Angle of Impact Calculations
Bloodstain Patterns
1. The harder and less porous the surface, the less the blood drop will
break apart.
2. The softer and more porous the surface, the more the blood drop will
break apart.
3. The ______________ of the bloodstain faces the ________________
Types of Blood Stain Patterns
1. Radial Pattern
– ____________________________________________________
2. Pooling
– ____________________________________________________
3. Arterial spurts
– ____________________________________________________
4. Cast-off (arc)
– Blood from weapon casts off onto ceilings, walls in preparation for
another blow.
5. Contact (transfer)
– ____________________________________________________
6. Trail
– ____________________________________________________
Area of Intersection and Convergence
1. The location of the blood source can be determined by drawing lines
from the various blood droplets to the point where they intersect.
2. The area of convergence is the point of origin—the _______________
________________________________________________________
3. It may be established at the scene by measurement of angles with the
use of ________________.
4. Lines are drawn through the ___________________ of blood stains.
5. More than one point of convergence indicates ___________________
________________________________________________________
Blood Evidence
1. Class evidence – __________________________________________
2. Individual evidence – _______________________________________
3. Bloodstain patterns are considered ____________________________
in a courtroom.
4. 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
Secretors
1. ______________________ of the population are secretors.
2. Their ____________________ are found in high concentration in their
body fluids such as saliva, semen, vaginal secretions, and gastric
juices.
People in the News
Herbert L. MacDonell
1. considered by many to be the ________________________________
________________________________________________________
2. is the director of the Lab of Forensic Science and founder of the
Bloodstain Evidence Institute (1973) in Corning, NY.
3. His book ________________________________________helped to
jump-start this discipline.
4. He has consulted on criminal cases in all 50 states, in addition to
testifying in the _____________________ trial and in the
assassination cases of ______________________________________
& ______________________________________________________