Chapter 8 Blood and Blood Splatter By the end of this chapter you will be able to: Explain the composition of blood Describe the function of blood cells Determine the blood type of a blood sample Conduct a blood splatter analysis Examine wounds and describe the nature of the weapon Find and process blood evidence

Introduction and History Blood typing provides class evidence DNA profiling provides individual evidence A blood splatter 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

Blood History – studied for thousands of years! Date Who Contribution 1628 Sir William Harvey Noted continuous circulation within the body 1874 Sir William Osler Discovered platelets 1901 Karl Landsteiner Discovered types: A, B, O 1940 Discovered Rh protein 1959 Dr. Max Perutz Described structure of hemoglobin 1971 Dr. Blumberg Developed method of antibody detection 1987-2002 Various Blood screening tests for infectious diseases

Composition of Blood Blood is a circulating tissue consisting of: Red blood cells (Erythrocytes)—carries oxygen to the body’s cells and carbon dioxide away White blood cells (Leukocytes)—fights disease and foreign invaders and, alone, contain cell nuclei Platelets (Thrombocytes)-aids in blood clotting and the repair of damaged blood vessels Plasma—a liquid suspending other blood components

Composition of Blood

Cellular Components of Blood The immune system functions to protect our bodies by identifying cells or molecules that are foreign, such as viruses, bacteria, and other parasites. White blood cells secrete proteins, antibodies that assist in the immune response.

Blood Typing—Proteins 1982 white blood cells were used as a source of DNA by Dr. Alec Jeffreys to produce the first DNA profile Discovered in 1900 by Karl Landsteiner – blood cannot be freely mixed with anothers blood Identifies the presence or absence of particular proteins embedded in the cell Quicker and less expensive than DNA profiling Produces class evidence but can still link a suspect to a crime scene or exclude a suspect

Blood Enzymes Enzymes are complex proteins that catalyze different biochemical reactions Many enzymes and proteins have been found in the blood that are important for identification purposes The more enzymes available for testing, the easier it will be to identify a person. Examples: Phosphoglucomutase (PGM) Adenylate kinase (AK) Adenosine deaminase (ADA) Esterase D (EsD) Glucose-6-phosphate dehydrogenase (G-6-PD) Haptoglobins (Hp)

Blood Typing —Probability and Blood Types 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%) Knowing additional proteins and enzymes in the blood sample Narrows the population group Increases the probability of identifying a suspect A 42% B 12% AB 3% O 43% MM 30% MN 48% NN 22% Rh+ 85% Rh- 15% Hp-1 14% PGM-2 6%

Probabilities What percentage of the population has A+ .42 X .85 = .357 35.7% Therefore about 36 out of every 100 people What percentage has O- ,MN .43 X .15 X .48 = .031 3.1% of the population! What percentage has A,NN,Hp-1,Rh-,PGM-2 .42 X .22 X .14 X .15 X .06 = .000116 .0116 % of the population Again, by testing for more blood-type proteins, the probability for uniqueness continues to increase, and the number of other people with the same combination as our suspect decreases.

Blood Typing—Antibodies Agglutination – clumping occurs when one arm of the Y shaped antibody attaches to the red blood cell, the second arm attaches to another red blood cell. Blood Typing—Antibodies Antibodies are Y-shaped proteins secreted by white blood cells that attach to antigens to destroy them Antigens are foreign molecules or cells that react to antibodies Ex. Viruses, bacteria, red blood cells from another person **There are more than 300 know blood group proteins and more than 1 million different protein binding sites on each red blood cell.

Blood Typing—Proteins 42% 12% 3% 43% of the population in the United States If a person contains only protein A = A blood If a person contains only protein B = B blood type If the person’s blood has both the A and the B proteins, then he or she has type AB blood.

Rh Factor 85% of the population has a protein called RH factor on their blood cells People with Rh+ can get Rh+ and Rh- Rh- can only get Rh-

Blood Typing Blood Typing

Blood typing!

Blood Typing The Blood Typing Game

Blood Typing Antibodies fight antibodies Donor Receiver 0 0 A A B B 0 0 A A B B AB AB Blood group A A antigens on the surface of your red blood cells and B antibodies in your blood plasma. Blood group B B antigens on the surface of your red blood cells and A antibodies in your blood plasma. Blood group AB A and B antigens on the surface of your red blood cells and no A or B antibodies at all in your blood plasma. Blood group 0 neither A or B antigens on the surface of your red blood cells, have both A and B antibodies in your blood plasma. Activity: Blood typing

Blood Spatter

Blood Splatter 1939—splatter patterns first analyzed Today, blood spatter evidence is used to explain events at a violent scene Blood may splatter when a wound is inflicted Blood splatter pattern—a grouping of blood stains Patterns help to reconstruct the events surrounding a shooting, stabbing, or beating

Blood Splatter Analysis Analysis of a splatter 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

Blood Splatter Analysis Natural cohesiveness of blood

Blood Splatter Analysis Satellite droplets— When blood falls from a height, or at a high velocity, It overcomes its natural cohesiveness, and separates from the main droplet Spiking patterns— Form around the droplet edges when blood falls onto a less-than-smooth surface Activity: Height (8-3)

Blood Splatter Analysis —Six Patterns Describe each of these: Passive drops - dropped at 90 degrees Arterial gushes - walls or ceilings cause by pumping Splashes - exclamation point Smears – bleeding victim leaving blood as they brush against something Ex. wall Trails - bleeding victim moving locations Pools – bleeding heavily and remaining in one place

Blood Descriptions Round – dropped at 900 Tails or satellites – determine direction Spatter – type of pattern >3mm Low velocity 1-3mm Medium Velocity <1mm High Velocity fine mist – high velocity impact EX. Gunshot Cast off –lower velocity EX. Hit with bat Voids – person was moved

Blood Splatter Analysis —Impact Patterns can help investigators determine the type of weapon used What kind of a pattern is produced by a gun shot? What kind of a pattern is produced by a hammer blow?

Blood Splatter Analysis —Directionality Adhesion – force between two unlike surfaces Surface tension -elastic characteristic along the outer edge of a liquid caused by the attraction of like molecules 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? Activity: Angles (8-4)

Blood Splatter Analysis Lines of convergence—two or more blood splatters can pinpoint the location of the blood source Activity: Area of Convergence (8-5) Point of Origin (8-6)

Crime Scene Investigation of Blood Search for blood evidence Determine Is the evidence blood? Is the blood human? What is the blood type? Interpret the findings: Does the blood type match a suspect’s blood? If not, exclude that suspect If yes, decide if DNA profiling is necessary

. . . . . . . . . . . . . . . . . Summary Blood consists of cellular components and plasma. 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. Blood splatter evidence can be used to recreate a crime scene. Investigators endeavor to (a) locate, (b) identify, and (c) interpret blood splatter patterns at crime scenes.