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Thursday, March 20, 2014

Criminal Justice Quote: Blood Spatter Patterns

     Drip and flow patterns are the infamous O.J. Simpson patterns that became known worldwide. A drip pattern occurs when a drop of blood drips into another liquid, usually more blood. If a person is bleeding and the drops are hitting an already formed puddle on the floor, a drip pattern will result. A flow pattern is blood that has been dropped in a trail. Though these types of patterns can be caused by other occurrence, they are traditionally represented by someone bleeding on the move, fleeing the scene of a crime.

     Splashed stains are similar to drip stains, though usually a little larger. They result from blood being projected with little force exerted on them and they usually disperse in a radial pattern. Think of splashing in terms of a mud puddle. If you jump in the puddle, the mud splashed in a radial pattern away from itself….

     Projected patterns are associated with a larger volume of blood that is acted upon with a significant amount of force. One of the classic examples of this pattern is an arterial spurt, seen in violent crimes when there is sharp force trauma or, in other words, a stabbing or slashing. If the all-too-familiar jugular vein is slashed, it will most certainly create this pattern.

     Satellite patterns are created when blood that was originally part of a bigger stain leaves that stain through some type of force. A drop of blood that is flying through the air will not separate without another force acting upon it. Think of it in terms of dropping blood at a significant height. When the drop hits a surface, it goes through four actions: contact, dispersion, displacement, and collapse. When blood contacts a surface, it flattens out. If there is enough volume and force to break the surface tension of the blood drop when it hits, it will disperse, sending blood out in all directions. If the force is great enough, it will displace. The displaced blood leaves the original parent stain, causing what is called satellite spatter. Satellite spatter is merely small stains leaving a larger stain. Finally, the blood drop will collapse back on itself with the vast majority of the blood collecting back together….

     Cast-off patterns are patterns that are created by blood being slug off an object, such as a bloody baseball bat, that is in motion or when the object suddenly stops….These patterns are traditionally found in a linear fashion, representing a swinging or chopping motion, and can help define where a person was when the pattern was created….These patterns are one of the three patterns that have caused the most debate among the bloodstain experts….

Jarrett Hallcox and Amy Welch, Bodies We've Buried, 2006  

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