1. Forensic Science: Fundamentals & Investigations, Chapter 8 1 Chapter 8 Blood and Blood Spatter By the end of this chapter you will be able to: o Explain the composition of blood o Describe the function of blood cells o Determine the blood type of a blood sample o Conduct a blood spatter analysis o Examine wounds and describe the nature of the weapon o Find and process blood evidence All Rights Reserved South-Western / Cengage Learning © 2012, 2009

2. Forensic Science: Fundamentals & Investigations, Chapter 8 2 Introduction and History o Blood typing provides class evidence o DNA profiling provides individual evidence o A blood spatter pattern provides information the truthfulness of an account by a witness or a suspect the origin of the blood the angle and velocity of impact the type of weapon used

3. Forensic Science: Fundamentals & Investigations, Chapter 8 3 Composition of Blood o Plasma—a liquid suspending other blood components o Red blood cells (Erythrocytes)—carries oxygen to the body’s cells and carbon dioxide away o White blood cells (Leukocytes)—fights disease and foreign invaders and, alone, contain cell nuclei o Platelets—aids in blood clotting and the repair of damaged blood vessels

4. o 55% Plasma 92% of plasma is made up of water 8% are other substances such as ions, hormones, glucose 45% Formed Elements 99 % of F. E. are red blood cells (RBC’s) 1% called the buffy coat are white blood cells (immunity) and platelets (clotting) Forensic Science: Fundamentals & Investigations, Chapter 8 4

5. 5 Composition of Blood

6. Forensic Science: Fundamentals & Investigations, Chapter 8 6 Types of White Blood Cells

7. Forensic Science: Fundamentals & Investigations, Chapter 8 7 Blood Typing—Proteins o Discovered in 1900 by Karl Landsteiner o Identifies the presence or absence of particular proteins embedded in the cell o Quicker and less expensive than DNA profiling o Produces class evidence but can still link a suspect to a crime scene or exclude a suspect

8. Forensic Science: Fundamentals & Investigations, Chapter 8 8 Blood Typing—Antibodies o Antibodies are Y-shaped proteins secreted by white blood cells that attach to antigens to destroy them. 2 types: Anti-A (fights A antigens) and Anti-B (fights B antigens) Antigens are proteins on the surface of some RBC’s that react to antibodies Two types: A antigens & B antigens

9. Forensic Science: Fundamentals & Investigations, Chapter 8 9 Blood Typing—Proteins 42%12%3%43% of the population in the United States antigens

10. Which is the rarest blood type? o http://www.redcrossblood.org/learn-about- blood/blood-types http://www.redcrossblood.org/learn-about- blood/blood-types Forensic Science: Fundamentals & Investigations, Chapter 8 10

11. blood types  There are 4 major blood types: A, B, AB, & O. Our blood plasma produces _____________against blood that is not our own, except for the ________blood type. BLOOD TYPE ANTIGENANTIBODIES PRODUCED CAN DONATE TO CAN RECEIVE FROM ABO AGGLUTINATION (CLUMPING) ANTI-A ANTI-B WELL PLATES A B %

13. Forensic Science: Fundamentals & Investigations, Chapter 8 13 Rh Factor 85% of the population has a protein called RH factor on their blood cells

14. Forensic Science: Fundamentals & Investigations, Chapter 8 14 Blood Enzymes o Enzymes are complex proteins that catalyze different biochemical reactions o Many enzymes and proteins have been found in the blood that are important for identification purposes

15. Forensic Science: Fundamentals & Investigations, Chapter 8 15 Blood Typing —Probability and Blood Types o The probability of a blood type equals the product of probabilities for each protein group If Type A = 42% and Rh Factor = 85% Then A+ =.42 x.85 =.357 (35.7%) o Knowing additional proteins and enzymes in the blood sample Narrows the population group Increases the probability of identifying a suspect

16. Forensic Science: Fundamentals & Investigations, Chapter 8 16 Blood Spatter o http://www.youtube.com/watch?v=Od8YuwUT 794 Las Vegas real blood spatter experts http://www.youtube.com/watch?v=Od8YuwUT 794 o 1939—spatter patterns first analyzed o Blood may spatter when a wound is inflicted o Blood spatter pattern—a grouping of blood stains o Patterns help to reconstruct the events surrounding a shooting, stabbing, or beating

17. Forensic Science: Fundamentals & Investigations, Chapter 8 17 Blood Spatter Analysis Analysis of a spatter pattern can aid in determining the: direction blood traveled angle of impact point of origin of the blood velocity of the blood manner of death

18. Forensic Science: Fundamentals & Investigations, Chapter 8 18 Blood Spatter Analysis Natural cohesiveness of blood http://www.youtube.com/watch?v=qX7Fd_QNX Ys

19. Forensic Science: Fundamentals & Investigations, Chapter 8 19 Blood Spatter Analysis o Satellite droplets— When blood falls from a height, or at a high velocity, It overcomes its natural cohesiveness, and Separates from the main droplet o Spiking patterns— Form around the droplet edges when blood falls onto a less-than-smooth surface

20. Forensic Science: Fundamentals & Investigations, Chapter 8 20 Blood Spatter Analysis —Directionality The shape of an individual drop of blood provides clues to the direction from where the blood originated. How will the point of impact compare with the rest of a blood pattern?

21. Forensic Science: Fundamentals & Investigations, Chapter 8 21 Blood Spatter Analysis Lines of convergence—two or blood splatters can pinpoint the location of the blood source

22. Forensic Science: Fundamentals & Investigations, Chapter 8 22 Blood Spatter Analysis —Six Patterns Classify each of the following as passive or active, then choose the type: arterial spray/spurt, transfer, wipe or swipe, cast off, high velocity impact, med/low velocity impact, walking drip,

23. Forensic Science: Fundamentals & Investigations, Chapter 8 23 Blood Spatter Analysis —Impact Patterns can help investigators determine the type of weapon used o What kind of a pattern is produced by a gun shot? o What kind of a pattern is produced by a hammer blow?

24. Forensic Science: Fundamentals & Investigations, Chapter 8 24 Crime Scene Investigation of Blood 1. Search for blood evidence 2. Determine a. Is the evidence blood? b. Is the blood human? c. What is the blood type? 3. Interpret the findings: a. Is the blood type consistent with a suspect’s blood? b. If not, exclude that suspect c. If yes, decide if DNA profiling is necessary

25. Blood Spatter Clips o http://www.youtube.com/watch?v=J40wqqg_ 8Ww Dexter stringing http://www.youtube.com/watch?v=J40wqqg_ 8Ww o Stringing Stringing o Mark Winger Case: Reconstruction Using Blood Spatter Evidence Mark Winger Case: Reconstruction Using Blood Spatter Evidence Forensic Science: Fundamentals & Investigations, Chapter 8 25

26. Forensic Science: Fundamentals & Investigations, Chapter 8 26................. Summary o Blood consists of cellular components and plasma. o The various human blood types are caused by the presence or absence of A and/or B proteins on the surface of red blood cells. o Blood spatter evidence can be used to recreate a crime scene. o Investigators endeavor to (a) locate, (b) identify, and (c) interpret blood spatter patterns at crime scenes.