BLOOD SPATTER

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

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 2

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

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 3

BLOOD SPLATTER ANALYSIS

Natural cohesiveness of blood

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 4

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

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 5

BLOOD SPLATTER 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?

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 9

CALCULATING ANGLE OF IMPACT Mathematically, the angle of impact can be calculated by the equation and determining the inverse of Sine A:

Width of blood stain

Sin A = -----------------------------

Length of blood stain

CLASSIFYING IMPACT SPATTER The droplet size can be used to determine the speed in which the impact occurred Provides insight to crime but not specific events

IMPACT VELOCITY VS. SIZE OF DROPLET Low Velocity Spatter:

Drops with diameters of 4 mm or more normally produced by an applied force of up to 5 ft/sec.

Medium Velocity Spatter: Drops with diameters from 1-4 mm with an applied force of 5 to 25 ft/sec

High Velocity Spatter: Drops with diameters of less than 1 mm from an applied force of 100 ft/sec or faster.

BLOOD SPLATTER ANALYSIS—SIX PATTERNS

Describe each of these: a) Passive drops b) Arterial gushes c) Splashes d) Smears e) Trails f) Pools

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 13

IMPACT SPATTER

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?

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 15

CAST-OFF SPATTER

ARTERIAL SPURT SPATTER

EXPIRATED BLOOD PATTERNS An expirated blood pattern is created by blood that is expelled from the mouth or nose from an internal injury.

The presence of bubbles of oxygen in the drying drops or a lighter color as a result of dilution by saliva can differentiate a pattern created by expirated blood.

The presence of expirated blood gives an important clue as to the injuries suffered and the events that took place at a crime scene.

BLOOD SPLATTER ANALYSIS

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 20

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

GUNSHOT SPATTER

Gunshot spatter is fine forward spatter from an exit wound and back spatter from an entrance wound. However, the gunshot produces only back spatter if the bullet does not exit the body.

VOID PATTERNS

A void is created when an object blocks the deposition of blood spatter onto a target surface or object and the spatter is deposited onto the object or person instead.

TRANSFER PATTERNS

A contact or transfer pattern is created when an object with blood on it touches one that does not have blood on it.

SKELETONIZATION

The phenomenon of skeletonization occurs when the edges of a stain dry to the surface.

This usually occurs within 50 seconds of deposition of droplets, and longer for larger volumes of blood.

DOCUMENTING

Investigators should note, study, and photograph each pattern and drop to accurately record the location of specific patterns and to distinguish the stains from which laboratory samples were taken.

When photographing be sure to include a scale.

TECHNIQUES OF DOCUMENTATION Two techniques used to document bloodstain patterns are: Grid method

A grid of squares of known dimensions are set up over the entire pattern.

Perimeter ruler method A rectangular border of rulers is set up around each pattern and a smaller ruler next to each stain.

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. Does the blood type match a suspect’s blood?

b. If not, exclude that suspect

c. If yes, decide if DNA profiling is necessary

FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 8 30