Bloodstain Pattern Analysis: is the examination of the shapes, locations, and distribution of patterns of bloodstains, in order to provide an interpretation of the physical events that gave rise to their origin.
The following Information may be obtained from a proper Bloodstain Pattern Analysis: 1. Distance from the blood source to the target 2. Direction of travel and impact angles 3. Nature of the force used to cause the bloodshed 4. The object used to cause the bloodshed 5. Sequencing of multiple bloodshed events 6.Interpretation of contact or transfer patterns
When properly documented, bloodstain patterns found at the crime scene, or on a particular person's clothing, can be used to:
2. Determine if there is evidence of a struggle, or if the assault is "one sided" 3. Confirm or refute statements made by principles in the case: IE: Are stain patterns on a particular person's clothing consistent with accounts given by the victim, witness, or defendant?
Blood Flight Characteristics: Blood will not break up unless it is acted upon by force. The force must be great enough to overcome the surface tension of the blood Blood forms a spherical shape (perfect circular shape) almost immediately upon separating from the blood source. The spherical shape is caused by the surface tension of the blood. Surface Tension causes the blood drop to pull itself in; both horizontally and vertically. The blood drop will settle into a spherical shape, as a result of the surface tension. The surface tension will maintain the sphere shape of the blood drop until it impacts with the surface.
SPATTER VS TRANSFER: The simplest type of blood spatter analysis is determining spatters from transfers. Spatters are created when blood is acted upon by force, and travels through the air before landing on a target surface. Transfers occur when a blood source comes in direct contact with a target surface area.
TARGET SURFACE TEXTURE:
LOW FORCE (VELOCITY) IMPACT SPATTER/PASSIVE DROPS:
MEDIUM FORCE (VELOCITY) IMPACT SPATTER:
HIGH FORCE (VELOCITY) IMPACT SPATTER:
IMPACT SPATTERS: are a random pattern of spatter of varying sizes
It is important to note that the term "Velocity" does not measure the speed at which the blood is traveling, but rather is used to describe or measure amount of force applied to the blood, to cause it to spatter.
Angle of Impact: The steeper the impact, the more elliptical or elongated, the blood drop
Direction: The "tail" points to the direction of the blood drop
Angle of Impact
sine= width = 9mm length = 18mm
• it is a secondary force or event.
BACK SPATTER OR "BLOWBACK"
The amount of high force impact spatter created will depend upon the size or caliber of the bullet fired, as well as the distance from the gun to the target. The larger the bullet, or projectile, the greater the spatter. The closer to the target that the gun is fired...the great the spatter.
For a complete list of bloodstain pattern terms, as recommended by the Internation Association of Blood Stain Pattern Analysts. (IABPA), go to: http://www.iabpa.org/ These terms should serve as a guide, for those who work and teach in the field of Blood Stain Pattern Analysis. These terms are not meant to be all encompassing
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