Blood and Blood Splatter By the end of this unit 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 Blood typing provides class evidence More than one person has the same blood type A, B, AB, & O blood types Positive (+) or Negative (-) DNA profiling provides individual evidence

Introduction (cont.) 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

History- Blood has been studied for thousands of years

History- Blood has been studied for thousands of years

Composition of Blood Blood is a SUSPENSION of cells in a liquid Plasma—a liquid suspending other blood components Red blood cells (Erthrocytes)—carries oxygen to the body’s cells and carbon dioxide away

Composition of Blood White blood cells (Leukocytes)—fights disease and foreign invaders and, alone, contain cell nuclei Platelets—aids in blood clotting and the repair of damaged blood vessels

Review of Cell Structure Do you remember this? Where is the DNA located?

Composition of Blood

The Immune System Our bodies have the ability to discriminate between their own cells and molecules (self) and foreign invaders (non self). Identifies foreign cells or molecules (bacteria, viruses, and other parasites)

White Blood Cells White blood cells engulf and digest the invaders Other white blood cells secrete antibodies White blood cells are the ONLY blood cells with a nucleus What does this mean?

White Blood Cells

Cellular Components of Blood

Blood Typing—Proteins Discovered in 1900 by Karl Landsteiner (A, B & O) 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 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Typing—Proteins 42% 12% 3% 43% of the population in the United States A & B proteins located on the surface of some red blood cells (RBC’s) Type O blood has neither, Type AB has both

Rh Factor 85% of the population has a protein called Rh factor on their blood cells Discovered in 1940 by Alexander Weiner, while working with Rhesus monkeys. Blood can be Rh+ or Rh-

Blood Type Exercises Blood Groups, Blood Typing, and Blood Transfusions Handout Review of Mendelian Genetics & Genetics of Bloodtyping Handout Blood Typing “Whodunit” lab Forensic Science: Fundamentals & Investigations, Chapter 8

October 4, 2011 Objective: Forensic Science: Fundamentals & Investigations, Chapter 8

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

Aggutination When antibodies are present in the plasma and a cell with foreign antigens is introduced agglutination will occur. The Y-shaped antibody will attach to multiple antigens on different cells This will cause a clumping, preventing blood flow that can lead to death

Blood Spatter Watch CSI – Season 1, Episode 7 “Blood Drops” for introduction

Blood Splatter 1939—splatter patterns first analyzed 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

History of Blood-Spatter Analysis 1894 Pitorski wrote the earliest reference to blood-spatter analysis 1939 Balthazard analyzed the meaning of the spatter pattern 1955 Blood-spatter evidence used in the defense of Sam Shepard helping to exonerate him 1971 used as a tool in modern forensic examinations by Dr. MacDonnell

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

Properties of Blood Blood is a mixture, but it doesn’t separate easily It is mostly water and therefore has many of the same properties (remember from biology?!?) resulting from hydrogen bonding Cohesion – sticks to itself Adhesion – sticks to other stuff Surface tension – elastic outer edge

Blood Splatter Analysis Natural cohesiveness of blood results in circular/round drops On a smooth surface drops will be smooth and circular On a porous surface (cement, wood, paper, etc.) blood will form small spikes or extensions

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

6 Patterns/Classifications Passive fall - Blood falling directly to floor at 90° angle results in: circular drops, with satellites if texture surface Arterial spurts/gushes – found on walls or ceilings, caused by pumping of heart Splashes – shaped like exclamation points, shape and position can give location of victim at time of attack Smears – left by victim as he/she touches or brushes against a wall or furniture Blood trails – left by victim as the move from one location to another (can be round, smeared, or spurts) Pools – form around a victim who is bleeding heavily and left in one location

Blood Splatter Analysis —Six Patterns Match each of these: Passive drops Arterial gushes Splashes Smears Trails Pools

Blood Splatter Analysis — type of wound Spatter patterns can help determine the type of wound Fine mist indicates high velocity impact (i.e. gunshot) Cast-off with lower-velocity pattern indicates beating (i.e. with a pipe) Voids (empty spaces) can determine presence of a person or an object moved after attack

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 Spatter pattern can be used to determine the angle of impact of droplets point of impact (or convergence) two-dimensional representation of location of the victim

Blood Splatter Analysis —Directionality Remember momentum? Darker due to its adhesive properties The shape of an individual drop of blood provides clues to the direction from where the blood originated. Tail points away from origin!! How will the point of impact compare with the rest of a blood pattern?

Blood Splatter Analysis Lines of convergence—two or blood splatters can pinpoint the location of the blood source

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.