Chapter 8 Blood and Blood Splatter By the

Chapter 8 Blood and Blood Splatter By the end of this chapter you will be able to: l explain the composition of blood l describe the function of blood cells l determine the blood type of a blood sample l conduct a blood splatter analysis l examine wounds and describe the nature of the weapon l find and process blood evidence All Rights Reserved South-Western / Cengage Learning © 2009 1 Forensic Science: Fundamentals & Investigations, Chapter 8

Genetic Terms to Remember l l 2 Phenotype- a set of observable characteristics of an individual Genotype- the genetic constitution of an individual Homozygous- having two of the same gene (either dominant or recessive) Heterozygous- having one dominant and one recessive copy of a gene Forensic Science: Fundamentals & Investigations, Chapter 8

Introduction and History Blood typing can provide class evidence; whereas DNA profiling can provide individual evidence. l A blood spattern can give information about the truthfulness of an account by a witness or a suspect. l It also can provide information about the origin of the blood, the angle and velocity of impact, and type of weapon used. l 3 Forensic Science: Fundamentals & Investigations, Chapter 8

Composition of Blood l Whole blood carries cells and plasma—the fluid 4 with hormones, clotting factors, and nutrients. Shown above respectively: l Red blood cells carry oxygen to the body’s cells and carbon dioxide away. l White blood cells fight disease and foreign invaders and, alone, contain cell nuclei. l Platelets aid in blood clotting and the repair of damaged blood vessels. Forensic Science: Fundamentals & Investigations, Chapter 8

How do you get your blood type? l There are 4 major blood types and 2 different antibodies: – – l 5 A, B, AB, and O Anti-A and Anti-B You get your blood type from your parents. You can determine the possible blood types for an individual if you know the blood types of their parents. Forensic Science: Fundamentals & Investigations, Chapter 8

How do you get your blood type? l l 6 Your blood types is a phenotype, but some blood types can have multiple genotypes. Blood types A and B are dominant over O (recessive), but A and B are co-dominant with each other Phenotype Genotype Antibodies A AA or AO Anti-B B BB or BO Anti-A AB AB None O OO Anti-B and Anti-A Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Typing—Proteins 42% 12% 3% of the population in the United States (of which 85% is Rh+) Blood typing is quicker and less expensive than DNA profiling. l It produces class evidence but can still link a suspect to a crime scene or exclude a suspect. l 7 43% Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Typing—Antibodies; Additional Proteins and Enzymes l Antibodies are proteins secreted by white blood cells that attach to antigens to destroy them. l Antigens are foreign molecules or cells that react to antibodies. l Enzymes are complex proteins that catalyze different biochemical reactions. l Many enzymes and proteins have been found in the blood that are important for identification purposes. 8 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Typing—Probability and Blood Types l Given the frequency of different genes within a population, it is possible to determine the probability that a particular blood type will appear in a particular population. l To determine the probability of two separate events, it is necessary to multiply their individual probabilities. l By identifying the additional proteins in the blood evidence sample, investigators can limit the size of a suspect population and help identify a suspect. 9 Forensic Science: Fundamentals & Investigations, Chapter 8

Practice Probability l 10 A man who is heterozygous Type A marries and woman who is heterozygous Type B. What are the possible phenotypes and genotypes of their children? Genotype Phenotype B O AB AB AO AO A O BO OO BO B OO O Forensic Science: Fundamentals & Investigations, Chapter 8

The Rh Factor l l 11 Red blood cells carry proteins on their surfaces in addition to anti-A and anti-B. The Rhesus factor, Rh, is a protein carried by some individuals. If a person carries the Rh factor they are “Rh positive. ” If not, they are “Rh negative. ” Rh is a dominant trait, so only one copy of Rh+ is need for a person to be Rh+. Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter In 1939 the meaning of the spattern was first analyzed. l When a wound is inflicted, a blood spattern may be created. l It takes a grouping of blood stains to make a blood spattern. l The pattern can help to reconstruct the events surrounding a shooting, stabbing, or beating. l 12 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis of a spattern can aid in determining the: – direction blood traveled. – angle of impact. – point of origin of the blood. – velocity of the blood. – manner of death. 13 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis l When blood falls from a height or at a high velocity, it can overcome its natural cohesiveness and form satellite droplets. l When it falls onto a less-than-smooth surface, it can form spiking patterns around the drops. 14 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Passive Patterns l 15 Passive Drop- Bloodstain drop(s) created or formed by the force of gravity acting alone. Produces circular drops with secondary satellites being more produced if the surface hit is textured Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Passive Patterns l 16 Drip Pattern- A bloodstain pattern which results from blood dripping into blood Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Passive Patterns l 17 Flow Pattern- A change in the shape and direction of a bloodstain due to the influence of gravity or movement of the object Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Projected/Impact Spatter l 18 Arterial Spurting (gushes)- bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery. Caused by the beating of the heart. Typically found on walls or ceilings. Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-splashes l Splashes are shaped like exclamation points. The shape and position of the spattern can help locate the position of the victim at the time of attack. 19 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-blood smears l 20 Smears are left by a bleeding victim depositing blood as he/she touches or brushes against a wall or furniture. Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-blood trails l 21 Trails of blood can be left by a bleeding victim as he/she moves from one location to another. The droplets could be round or smeared or even appear as spurts. Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Passive Patterns l 22 Pools- a bloodstain pattern created when a source of blood remains stationary over a surface causing an accumulation of blood. If the bleeding victim moves to another location, there may appear to be droplets or smearing connecting the first location with the second. Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Passive Patterns l 23 Saturation- A bloodstain pattern created when a volume of blood has been absorbed by an object Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Transfer Patterns l 24 Transfer/Contact Pattern- a bloodstain pattern created when a wet, bloody surface comes in contact with a second surface. A recognizable image of all or a portion of the original surface may be observed in the pattern Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Transfer Patterns l 25 Swipe Pattern- The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered edge Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis-Transfer Patterns l 26 Wipe Pattern- A bloodstain pattern created when an object moves through an existing stain, removing and/or altering its appearance Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Projected/Impact Spatter l 27 Cast-off Pattern- a bloodstain pattern created when blood is released or thrown from a blood-bearing object Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Projected/Impact Spatter l 28 Expirated Blood- Blood that is blown out of the nose, mouth, or a wound as a result of air pressure and/or air flow which is the propelling force. Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Directionality l Cohesion- a force between two similar substances. l Adhesion- a force between two unlike surfaces, such as blood and a wall. l Surface tension- an elastic characteristic along the outer edge of a liquid caused by the attraction of like molecules. 29 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Splatter Analysis —Directionality The shape of an individual drop of blood provides clues to the direction from where the blood originated = direction the blood is traveling This can be determined by measuring the point of origin of the droplet. How will the point of impact compare with the rest of a blood pattern? 30 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Projected/Impact Spatter l 31 Low Velocity Impact Spatter (LVIS)- A bloodstain pattern that is caused by a low velocity impact/force to a blood source Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Projected/Impact Spatter l l 32 Medium Velocity Impact Spatter (MVIS)- a bloodstain pattern caused by a medium velocity impact/force to a blood source. A beating typically causes this type of spatter Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Projected/Impact Spatter l l 33 High Velocity Impact Spatter (HVIS)- a bloodstain pattern caused by a high velocity impact/force to a blood source Often produced by a gunshot or high speed machinery Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Miscellaneous l l 34 Void- an absence of stain in an otherwise continue bloodstain pattern Indicates that a person or object was in the way of the blood spatter and was later moved Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis. Miscellaneous l 35 Skeletonized Stains- a bloodstain consisting of a darkened peripheral rim where the center of the stain is no longer intact Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Droplet Characteristics l l 36 A blood droplet will remain spherical in space until it collides with a surface. The spherical shape is caused by the surface tension of the blood. Forensic Science: Fundamentals & Investigations, Chapter 8

Angle of Impact l The shape of a blood drop: – – 37 Round- if it falls straight down at a 90 degree angle Elliptical- blood droplets elongates as the angle decreases from 90 to 0 degrees Forensic Science: Fundamentals & Investigations, Chapter 8

Determining the Angle of Impact l 38 Angle of impact= sin-1(width/height) Forensic Science: Fundamentals & Investigations, Chapter 8

Determining Angle of Impact l l 39 Make sure your calculator is in degrees! Example: Width= 3 mm, Length= 5 mm Angle= Sin-1(3 mm/5 mm) Angle = 37 degrees Forensic Science: Fundamentals & Investigations, Chapter 8

Origin of the Blood l l 40 Lines of convergence Draw straight lines down the axis of the blood spatters. Where the lines converge, the blood originated. Forensic Science: Fundamentals & Investigations, Chapter 8

Determining Point of Origin 1. 2. 3. 4. 5. 41 6. Place the ring stand on area of convergence Write the calculate angle of impact next to each stain. Using string, tape, and a protractor, raise the string to the calculated angle and attach it to the ring stand. Do the same for multiple stains. The place on the ring stand where the string from each stain meets is the area of orgigin Measure the height of the area of origin Forensic Science: Fundamentals & Investigations, Chapter 8

Search for blood evidence: 1. A stain could be ketchup, red ink, or other substance. Make sure it’s blood before you collect it! a. Kastle-Meyer test- if blood is present, a dark pink color is produced. b. Leukomalachite Green- if blood is present, a green color is produced. 42 Forensic Science: Fundamentals & Investigations, Chapter 8

Crime Scene Investigation of Blood 2. If any blood is discovered, process it determining: a. Whether the evidence is blood. b. Whether the blood is human. (ELISA test) c. The blood type. 3. Interpret the findings: a. See if the blood type matches a suspect. b. If it does not, exclude that suspect. c. If it does, decide if DNA profiling is needed. 43 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis l 44 http: //www. youtube. com/watch? v=J 40 wqqg_ 8 Ww Forensic Science: Fundamentals & Investigations, Chapter 8

. . . . Summary l Blood consists of cellular components and plasma. l The various human blood types are caused by the presence or absence of A or B or both A and B proteins on the surface of red blood cells. l Blood splatter evidence can be used to recreate a crime scene. l Investigators endeavor to (a) locate, (b) identify, and (c) interpret blood splatter patterns at crime scenes. 45 Forensic Science: Fundamentals & Investigations, Chapter 8