Final - Blood Stain Patterns

Documenting Bloodstain Evidence

*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

Swipes

A pattern caused by a bloodstained object coming into contact though lateral motion with another object which is not bloodstained Aka a *transfer stain in motion*

Wipes

A pattern caused by an object coming into contact through lateral motion with a pre-exisisting bloodstain on another object Skeletonization of the original bloodstain

Blood Pool

An accumulation of blood Without any specific shape, but conforming to the surface contours It may demonstrate serum separation (separation of the blood cells from the plasma) *Collect white blood cells for DNA analysis*

Arterial Spray Spatter

Caused by an injury to the heart or a main artery and the pressure of the continuing pumping Site of the initial injury to the artery can be found there the pattern begins with the *biggest spurt*, the trail away from this point shows the victim's movement The oxygenated blood spurting from the artery tends to be brighter red color than blood expelled form impact wounds Spike pattern (similar to EKG)

PAB (Physically Altered Bloodstain) Principle

Exposed blood will react to environmental conditions (e.g., air flow, temperature, humidity, variations of surface) in a predictable manner.

Blood Flow

Follows gravity Can indicate that an object was moved while the blood was flowing

Gunshot Spatter

Forward spatter from an exit wound and back spatter from an entrance wound The gunshot produced ONLY back spatter if the bullet does not exit the body

Skeletonization

Occurs when the edges of a stain dry to the surface Usually occurs within 50 seconds of deposition of droplets, and longer for large volumes of blood Knowing the skeletonization time, an investigator can determine the timing of movement or activity

Transfer Patterns

Result from the transfer of blood from one object to another without lateral motion EX: footwear impressions Stains will diminish in the direction of travel as a bloodstained object leaves transfer pattern repetitively

Mathematic Equation for Directionality and Angle of Impact

Sin A = Width of Blood Stain/Length of Blood Stain

Spatter Stain vs. Non-Spatter Stain

Spatter Stains are small circular and elliptical shaped stains Non-Spatter Stains are everything else

Blood into Blood Pattern

Surrounded by random distribution of small spatter The spatter will generally not have consisted directional angles

Directionality and Angle of Impact

The direction of travel of blood striking an object may be discerned because *the pointed end of a bloodstain always faces its direction of travel* At right angles (90 degrees) the blood drop is circular; as the angle decreases, the stain becomes elongated.

Effects of Surface Texture

The harder and less porous the surface, the less spatter results. Rough surfaces (concrete, wood) usually result in irregular shapes with serrated edges, possibly with satellite spatter and more spatter

Bloodstain Pattern Interpretation may uncover:

The movement of a bleeding individual at the crime scene The approximate number of blows that struck a bleeding victim The approximate location of an individual delivering blows that produced a bloodstain pattern The direction from which blood originated The angle at which a blood droplet struck a surface The location or position of a victim at the time a bloody wound was inflicted

Area of Convergence

The point on a two-dimensional plane from which the drops in an impact pattern originated

Point of Convergence

The point where the reverse vectors of several related spatter stains converge on a surface (ex: the floor)

The Principle of Stain Shape and Vector Correlation

The shape of a bloodstain provides indicators as to the direction of deposition as well as the spatial origin of the blood. Sub principles are Impact , Directional Angle and AO

Pattern Diversity Principle

The variations in combinations of blood volumes and forces acting on those volumes lead to recognizable classes of patterns.

Satellite Patterns

These patterns arise from blood droplets that leave the parents stain by some degree of force

Area of Origin

An impact bloodstain pattern is the area in a three-dimensional space from which the blood was projected (aka where did the blood spatter originate from) This will show the position of the victim or suspect in space when the stain-producing event took place (the string method)

Rules for Determining Directionality of Swipes and Wipes

Blood dries in the direction of travel and becomes "gritty" Volume is displaced (pushed) in the direction of travel

Expectorate Blood Patterns

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 exported blood

Cast-off Spatter

Created when a blood-covered object flints blood in an arc onto a nearby surface Commonly produced by a bloody fist or weapon between delivery blows The features of cast-off pattern are affected by the *size of the object, the amount of blood, and the direction the object was moving* One may determine the minimum number of blows delivered

Void Patterns

Created when an object blocks the deposition of blood spatter onto a target surface or object and the spatter is deposited onto the object of person instead

Contact/Transfer Patterns

Created when an object with blood on it touches one that does not have blood on it

Use of Luminol Detecting Bloodstain Patterns

Discovering wipes and swipes present on floors and walls (signs of a clean up) *Checking scene of suspicious disappearances for indications of clean-up*

Impact Bloodstain Spatter

Impact spatter occurs when an object impacts a source of blood

Spurt Pattern

Large elliptical stains Line of stains or overlapping stains oriented in Vs, arcs or serpentine patterns

Velocity of Impact Spatter

Low velocity impact spatter can be characterized by stains of *4mm or more* normally produced by an applied force of *up to 5ft/sec* (associated with minimal force) Medium velocity spatter can be characterized by stains of *1-4mm in diameter* normally produced by an applied force of *5 to 25 ft/sec* (associated with blunt force trauma) High velocity spatter can be characterized by stains *less than 1mm in diameter* normally produced by an applied force of *100 ft/sec or faster* (associated with gun shot wounds or explosions)