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Published byReynard Cole Modified over 8 years ago
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The use of physics and math to interpret bloodstain patterns within a forensic setting May show: 1. Activity at scene 2. Number of blows 3. Position of victim and assailant 4. Whether death was immediate or delayed 5. Weapon characteristics
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1894 - Pitorowski wrote earliest reference to bloodstain pattern analysis 1939 - Balthazard was first to use physical interpretations of stains 1955 - Dr. Paul Kirkused bloodstain pattern interpretation as a defense witness in the Sam Shepherd case 1971 - Professor Herbert MacDonnell promoted bloodstain pattern interpretation as a tool for modern criminalistics 1983 – The International Association of Bloodstain Pattern Analysis was formed
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Package in NON-air tight container, such as a paper bag, so that no mold grows— dry blood can still be analyzed
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Circulates throughout body to transport oxygen, electrolytes, nourishment, hormones, vitamins, and antibodies to tissues an organs Contains red blood cells (erythrocytes), white blood cells (leukocytes), plasma, and platelets Held together by STRONG cohesive forces
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Does NOT fall in tear drop form (spherical) Will not break apart as it falls through air Is 6 times more viscous than water Has average volume of 0.05 ml (diameter = 4.56 mm) Blood hitting surface --hard smooth surface = creates little spatter --wood or concrete = create larger spatter (fig. 11.2, pg. 192) Spattered blood = random distribution of bloodstains
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Allows for determination of area or location of origin of blood source (triangulation—see picture) Place someone at a crime (on clothing) ***May determine mechanism that created pattern (including speed of drop at impact, weapon used, direction of travel, angle of impact,)***
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Notice the “top view”!
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LVIS—low impact velocity impact Force = up to 5ft/sec diameter= 4 mm+ Examples: blood drops into blood and footstep spatters
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MVIS—medium velocity impact Force = 5-25 ft/sec diameter = 1-3 mm Examples: blood flicked off finger and blunt object used on victim
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HVIS—high velocity impact Force = +100 ft Diameter = < 1mm Examples: gunshots and propellers
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Impact spatters: 1-Gunshot—mistlike pattern (<1mm blood spots) --Size range dependent on amount of blood, caliber of weapon, # of shots and location on body, hair/clothes --blowback or back spatter possible 2-Beating or stabbing—sizes 1-3 mm --depends on force and quantity of blood --only exposed blood makes spatter (not 1 st blow) --type of weapon influences pattern
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Direction of travel --Narrow end of elongated bloodstain points in direction of travel (impact angle < 90 degrees) --the tail will point in direction of travel --Circular bloodstain = no travel, dropped @ 90 degree angle
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Impact Angle calculation (for elliptical bloodstains) 1 st find ratio of width to length (see picture) Then take the arc sin of that ratio › Thus... Angle of impact = sin -1 (width/length)
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sin θ = W / L W L What does W = L mean? sin θ = 1 → θ = 90 Drop is a circle!
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90 degrees – 60 degrees – 30 degrees – 10 degrees –
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Closer for high velocity spatter or when stains originate closer to where the spatter occurred
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Rule of Thumb: As impact angle goes down, bloodstain shape becomes more elongated.
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String Convergence in a 2 Dimensional Plane Convergence
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Transfer patterns (gun, knife, hand, foot…) Void patterns (indicating some object was removed or a person was hit by spatter) Flow patterns (may indicate movement with change in flow)
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Satellite or secondary spatter = single drops, circular or oval, 0.1=1 mm size Drip pattern = multiple, free falling drops on horizontal surface Castoff pattern = multiple blows to same area where wound has occurred and blood has accumulated
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Expirated patterns = blood that has pooled in lungs, sinuses, or airway passages is expelled from body Arterial patterns = breaching of artery and result is gushing or spurts of blood Blood transfer pattern = blood stained object contacts unstained object (can be a smear) Dried blood = color changes... red –to— reddish brown —to— black
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Clotting time outside the body ranges from 3 – 15 minutes Spattered clots indicate that time passed between the initial bleeding and later blows Coughing of clotted blood may indicate post-injury survival of victim
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Drying begins at periphery and proceeds inward Drying time is affected by › Surface type › Amount of blood › Climatic conditions Skeletonization › Partially dry stains leave a ring that outlines original spatter › The drier the stain, the less skeletonization shown
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Document size, shape, and distribution of stains and patterns Use photographs, video, diagrams, and notes Collect articles of evidence with significant or questionable patterns (Remember Luminol can be used to detect or enhance bloodstain patterns)
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