Blood Spatter Blood spatterns n Help to reconstruct

Blood Spatter

Blood spatterns n Help to reconstruct the series of events surrounding a shooting, stabbing or beating n First reference to blood spatter analysis was in 1894 n Blood spatter evidence was used by the defense in the Sam Shepard case in 1955 to help exonerate him.

Blood Spatterns n Makes it possible to determine: – the direction the blood was traveling – the angle of impact – the point of origin of the blood – The manner of death, based on blood velocity

Blood drops n Blood is a thick mixture of blood cells and plasma n When a person is bleeding, gravity acts on blood, pulling it downward, making it longer than it is wide n Blood is cohesive, so it “sticks together” and doesn’t separate as it falls n Blood maintains a round appearance when it falls on a flat surface

Satellites n Small secondary droplets that have overcome the force of cohesion and separated from the main droplet of blood

Six Patterns of Blood Spatter 1. Circular Drops – produced by blood falling directly to the floor at a 90 degree angle - secondary satellites will be produced if the surface is textured - this is known as passive fall

Patterns (continued) 2. Arterial spurts or gushes found on walls or ceilings - caused by the pumping action of the heart

Patterns (continued) 3. Splashes – shaped like exclamation points. - the shape and position of the spattern can help locate the position of the victim at the time of attack

Patterns (continued) 4. Smears – left by a bleeding victim depositing blood as he or she touches or brushes against a wall or furniture

Patterns (continued) 5. Trails – left by a bleeding victim as they move from one location to another - droplets could be round or smeared or even appear as spurts

Patterns (continued) 6. Pools of blood – form around a victim who is bleeding heavily and remains in one place

More Patterns n Fine mist – produced by high velocity impact, like a gunshot wound n Low velocity pattern – produced by a beating with a pipe n Voids – empty spaces in a spattern that help determine if something was moved after the attack

Examination of Directionality of Blood The shape of an individual drop of blood can provide important clues in an investigation. n As moving blood strikes a surface, several forces affect the droplet of blood: n – Cohesion – force between two similar substances – Adhesion – force between two unlike surfaces – Surface tension – an elastic characteristic along the outer edge of a liquid casued by the attraction of like molecules

Lines of Convergence The location from which the blood originated can be determined if there at least two blood spatters. n Draw straight lines down the long axis of the blood spatter and note where the lines intersect – this indicates the lines of convergence n

Crime Scene Investigation of Blood n Even after washing a room of visible blood, some blood evidence remains n Luminol – causes hemoglobin (the iron containing portion of the blood) to fluoresce under black light

Steps in Investigating Blood left at a Scene 1. 2. 3. 4. Confirm the stain is blood Confirm that the blood is human blood Determine the blood type Perform a DNA analysis if necessary and if DNA can be isolated from the sample