Blood Spatter Analysis

Bloodstain Pattern Analysis (BPA)

While the use of bloodstains as evidence is not new, the application of modern science has brought it to a higher level.

New technologies (DNA analysis) are available for detectives and criminologists to use in solving crimes and apprehending offenders.

Bloodstain Pattern Analysis (BPA)

BPA applies scientific knowledge from other fields to solve practical problems

Draws from biology, chemistry, math and physics

Produces strong, solid evidence

BPA can determine

Location and description of individual stains and patterns

Mechanism that created the stains Direction a blood droplet was traveling Area of origin Type of object used in attack Minimum number of blows Presence of a subject at a scene Positioning of the victim, suspect and

objects during events Sequence of events

Angle of Impact and Point/Area of Convergence

Determining angles of impact

Blood droplets in freefall have the shape of a sphere.

Droplets striking surfaces and leaving well-formed stains make it possible to determine the angle at which the droplet struck the surface.

Determining angles of impact

A well-formed stain is in the shape of an ellipse

L/W followed by taking the inverse sin (sin-1) gives the impact angle

Point and area of convergence

The point of convergence is the intersection of two different bloodstain paths

Point and area of convergence

The area of convergence is the box formed by the intersection of several stains from opposite sides of the impact pattern

Point and area of Origin

Point (Area) of Origin – the common point (area) in three dimensional space to which the trajectories of several blood drops can be retraced

TARGET SURFACE TEXTURE

Target surface texture

Bloodstains can occur on a variety of surfaces, such as carpet, wood, tile, wallpaper, clothing…..

The type of surface the blood strikes affects the amount of resulting spatter, including the size and appearance of the blood drops.

Target surface texture

Blood droplets that strike a hard smooth surface, like a piece of glass, will have little or no distortion around the edge.

Target surface texture

Blood droplets that strike linoleum flooring take on a slightly different appearance.

Notice scalloping around the edge of the blood droplets.

Target surface texture

Surfaces such as wood or concrete are distorted to a larger extent.

Notice the spines and secondary spatter present.

BLOODSTAIN PATTERN CATEGORIES

Bloodstain pattern categories

Classifies stains based on the mechanism that created them.Passive bloodstains - created when

gravity is the force acting upon it.Projected bloodstains- occur when

some form of energy has been transferred to a blood source

Transfer or contact- produced when an object with blood on it comes in contact with an object or surface that does not have blood on it.

PASSIVE BLOODSTAINS

Passive Drop

A bloodstain drop(s) created or formed by the force of gravity acting alone

Drip Pattern

A bloodstain pattern that results from blood dripping into blood

Flow Pattern

A change in the shape and direction of a bloodstain due to the influence of gravity or movement of the object

PROJECTED BLOODSTAINS

Low Velocity Impact (LVI)

Relatively large stains 4 mm in size and greater. Impact velocity up to 5 feet/sec

Medium Velocity Impact (MVI)

Preponderant stain size 1 to 4 mm size.Impact velocity of 5 to 25 feet/sec.

High Velocity Impact (HVI)

Preponderant stain size 1 mm in size and smaller. Mist like appearance.

Impact velocity of 100 feet/sec and greater.

Cast-off Pattern

A bloodstain pattern created when blood is released or thrown from a blood-bearing object in motion

Arterial Spurting or Gushing

Bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery

Back spatter – blood directed back towards the source of energy or force that caused the spatter

Expiratory 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

TRANSFER/CONTACT BLOODSTAINS

Swipe Pattern

The transfer of blood from a moving source onto an unstained surface. Direction of travel may be

determined by the feathered edge.

Hair swipe Pattern

The transfer of blood from a moving source onto an unstained surface. Direction of travel

may be determined by the feathered edge.

Wipe Pattern

A bloodstain pattern created when an object moves through an existing stain, removing

and/or altering its appearance.

Transfer Pattern

A recognizable image of all or a portion of the original surface may be observed in the pattern.

Transfer Pattern

A recognizable image of all or a portion of the original surface may be observed in the pattern.

Transfer Pattern

A recognizable image of all or a portion of the original surface may be observed in the pattern.

Transfer Pattern

A recognizable image of all or a portion of the original surface may be observed in the pattern.

Transfer Pattern

A recognizable image of all or a portion of the original surface may be observed in the pattern.

Transfer Pattern

A recognizable image of all or a portion of the original surface may be observed in the pattern.

Sources

BPA Tutorial http://www.bloodspatter.com/BPATutorial.htm

Blood Pattern Analysis (Wikipedia, I kid you not!) http://en.wikipedia.org/wiki/Blood_pattern_analysis_at_crime_scenes

International Association of B. P. Analysts http://www.iabpa.org/