CHAPTER 8. BLOOD TYPING
Forensic Science I
Chapter 8. Blood and Blood SpatterObjectives and Vocabulary
Objectives Explain the composition of
blood Describe the functions of
blood cells Describe a brief history of the
use of blood and blood spatter in forensics
Describe how to determine the blood type of a sample of blood
Calculate the probability of certain blood types within a population
Conduct a blood spatter analysis
Examine stab wounds and describe the nature of the weapon
Use blood spatter evidence to recreate the events of a crime scene
Vocabulary Agglutination Antibodies Antigen-antibody response Antigens Cell surface proteins Lines of convergence Point of origin Red blood cells Satellite drop of blood White blood cells
Chapter 8. Blood and Blood SpatterBlood Paints a Picture
1. Why did the police suspect that the wife did not fall and injure herself?
2. What would they need to find out about the bloodstain on the husband’s sleeve to validated their suspicions?
3. Was there other evidence the police could use to prove or disprove the husband’s story?
Chapter 8. Blood and Blood SpatterIntroduction
Blood typing, class evidence Type O Type A Type B Type AB
DNA DNA is found in white blood cells
Blood spatter Note the direction the blood originated The angle of impact Point of origin Low or high velocity impact Type of weapon used
Chapter 8. Blood and Blood SpatterBlood History
Blood has been studied in one way or another for thousands of years (See Figure 8-1)
Chapter 8. Blood and Blood SpatterComposition
Circulating Tissue made up of three types of cells Red blood cells
(RBC) White blood cells
(WBC) Platelets
Cells are suspended in liquid called plasma
Chapter 8. Blood and Blood SpatterBlood Cells
Red Blood cells Erythrocytes Carry respiratory gases Hemoglobin in red blood cells,
carries oxygen, gives blood its color
White Blood cells Leukocytes Fights disease and foreign
invaders Antibodies, secrete proteins Contain a nucleus
Platelets Thrombocytes Aid in blood clotting Help repair damaged blood
vessels
Chapter 8. Blood and Blood SpatterBlood Cells
Red Blood Cells 5-6 million
White blood cells 5,000-10,000
Platelets 250,000-400,000
Chapter 8. Blood and Blood SpatterBlood Typing
Blood typing is less expensive and quicker than DNA profiling
Considered class evidence because many people share the same type
Can link a suspect to the crime
Chapter 8. Blood and Blood SpatterDiscovery of Blood Types
1900, Karl Landsteiner Blood from one person
did not always freely mix with blood from another person
The presence or absence of cell surface proteins gives rise to our present system of blood typing.
Use an antibody reaction test
Chapter 8. Blood and Blood SpatterA and B proteins
A and B proteins are found on the surface of some red blood cells A proteins – A Blood B proteins – B Blood A and B proteins –
AB Blood No proteins – O
blood
Chapter 8. Blood and Blood SpatterA and B proteins
Percentage of the U.S. population Type O (43 %) Type A (42 %) Type B (12%) Type AB (3%)
Probability and Blood Types, pg 201
Chapter 8. Blood and Blood SpatterRh Factor
1940, Alexander Wenier- Discovered the Rh Factor
85% of the population has a protein called Rh factor , Rh+
Blood that does not have the protein is called Rh-
Chapter 8. Blood and Blood SpatterNaming of Blood Types
Based on presence or absence of the AB and Rh proteins
Difference of blood types was not discovered until 1901.
Antibodies will cause the blood to clump and may cause death.
Universal accepter
Universal donor
Chapter 8. Blood and Blood SpatterAntibodies
B-lymphocytes secrete antibodies Recognizes foreign
invaders Antibodies bind to
a the molecular shape of an antigen
Chapter 8. Blood and Blood SpatterAntigen-Antibody Response
Antigen-antibody response, when a foreign invader is recognized by the immune system
May be viruses, bacteria, or even the red blood cell protein from a person with a different blood type
Chapter 8. Blood and Blood SpatterAgglutination
Agglutination, when one arm of the y shaped antibody attaches to the red blood cell and the second arm attaches to another red blood cell
Could produce a clot in the blood vessel , will result in loss of gas exchange
Chapter 8. Blood and Blood SpatterBlood Typing Tests
Blood Typing http://nobelprize.org/
educational_games/medicine/landsteiner/index.html
C.S. #1-Ludwig Tessnow- 1901 Dismembered bodies of an eight and
six year old were found in the woods near their home.
Tessnow was a suspect and had blood on his clothes and boots. Told police they were from wood dye.
Based on blood test created by Paul Ihlenhuth--- found that he was guilty from the blood stains. Distinguish between animal and human
blood as well as other stains. Executed in prison.
C.S. #2-Thomas Zeigler 1975 Christmas Eve , found his wife, her
parents and citrus worker were found dead in his store.
Claimed that a gang attempted to rob the store.
However when a blood expert came in to examine the bodies, they figured out that Thomas did it.
Sentenced to life in prison.
Graham Backhouse ( 1985)-- accused of killing his neighbor and attempting to kill his wife. Claimed that the bomb was from his neighbor. When police got to the house, found that the neighbor was shot with gunshots. Backhouse had sustained wounds to the face and chest. Backhouses wounds were self inflicted from the blood spater. Backhouse was convicted of murder of his neighbor and the attempted murder of his wife.
C.S. #3-Graham Backhouse 1985 Accused of killing his neighbor and
attempting to kill his wife. Claimed that the bomb was from his
neighbor. When police got to the house, found
that the neighbor was shot with gunshots.
Backhouse had sustained wounds to the face and chest. Backhouses wounds were self inflicted from the blood spatter.
Backhouse was convicted of murder of his neighbor and the attempted murder of his wife.
Top Related