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Unformatted text preview: ush, cast-off, impact (low, medium, and high velocity) TRANSFER BLOODSTAINS A transfer bloodstain is created when a wet, bloody surface comes in contact with a secondary surface. PASSIVE BLOODSTAINS Passive bloodstains are drops created or formed by the force of gravity acting alone. PROJECTED BLOODSTAINS Projected bloodstains are created when an exposed blood source is subjected to an action or force, greater than the force of gravity (Internally or Externally produced). The size, shape, and number of resulting stains will depend, primarily, on the amount of force utilized to strike the blood source. Low Velocity (Gravitational pull up to 5 feet/sec., Relatively large stains 4mm in size and greater) High Velocity (Force of 100 feet/sec. and greater, Stains 1mm in size and smaller, Mist like) like) Medium Velocity (Force of 5 to 25 feet/sec., Preponderant stain size 1 to 4mm in size) Useful In Crime Scene Reconstruction
Though not always easy to find and/or recognize, important bloodstain patterns to note at a scene: Foot prints Hand prints Animal paw prints Shapes of items/tools Blood drops heading in a certain direction Blood on an item near or away from the source Bloodstains on the inside or outside of clothing? Spatter Basics Drop of blood is spherical If blood falls 90 to the impact surface spatter is circle Impact angles cannot be greater than 90 A "tail" may result which is not part of the impact ellipse Blood Spatter
To calculate the angle L =length of the ellipse W= width of the ellipse = angle of impact sin = (W/L) = arcsine (W/L)
.44" 1.17" = 22 Note: Results will be more correct if the ellipse is drawn in via computer. The length and width of the resulting can be obtained from typically right clicking and choosing the correct option (ie format picture and then size tab) Point of Convergence Example Point of Convergence Example
Gridding was used for documentation, with angle determination and string method to verify point of origin. All blood drops seem consistent with our known point of origin (Bob's head). What is Forensic Science? The application of science to law Forensic scientists provide scientific services to the legal system The law dictates how science can be used How experiments/analyses are conducted How evidence is handled What is admissible in court Justice System
Who? Identifying perpetrator Civil
Identifying who's at fault (involvement) Person was "most likely involved" Judge/Jury decide...
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- Winter '09