Transcript Slide 1
Blood Spatter Analysis Presented by Patricia Nolan Bertino Bud Bertino Blood Spatter (not splatter) is the pattern of blood created when blood is deposited on a surface. Blood Detection • Phenolphthalein • Luminol Blood spatter “tells a story” • Where was person located when bleeding? • What direction was blood traveling? • What was the angle of impact? What was the distance between bleeder and the striking surface? How many events occurred? Is blood spatter evidence consistent with the story told by witness or suspect? Simpson Crime Scene Types of Injury • High velocity (gunshot) • Medium velocity (hammer strike) • Low velocity ( drip) Characteristics of a single drop of blood Spike vs. Satellite Surface variations Smooth (glass) Slightly raised (floor tiling, varnished wood, fabric) Rough tile, unvarnished wood Types of Blood Spatter • Passive dripped blood • Transferred hand print • Projected artery bleed • Cast off from a weapon Transferred blood Footprint Handprint Projected blood Arterial gush on wall Blood dropped from different heights Patterns of transfer ceiling Cast-off from Weapon Direction of travel of blood Wave Cast-off Tail of elongated stain points in direction of travel . Tail of wave cast-off points back to parent drop Parent drop wave cast-off 5 ml blood squirted from a syringe from height of 1 m Point of Convergence Height above point of convergence Angle of Impact Origin length width Angle of impact = arc sin W/L 85 60 45 Distance from point of convergence 30 Angle of Impact W Path of blood 90 80 70 60 50 40 30 20 a l l Floor 10 Determine Angle of Impact Width Length sine arc sine 42° 2 3 .6667 1 4 .25 14.5° 9.6 9.7 .9897 82.2° Hand-out Point of Convergence Lines of Convergence • Draw line through the axis of the main droplet • Start at the end of the blood drop and draw toward the source • Do not draw lines through satellite drops • Draw smallest circle around intersection marks point of convergence Lines of Convergence Determine Point of Convergence Don’t over extend the lines! Draw towards the source of blood Let’s practice! Floor demo worksheet Answer Sheet for Lines of Convergence Show Blood animations Practice Paper Blood Droplets • • • • Draw lines of convergence Determine point of convergence Measure blood drop width/length Determine impact angle Can you determine point of origin? Calculate Point of Origin •Draw lines of convergence •Determine point of convergence •Determine impact angle Floor demo •Use protractor to determine origin Or Use Law of Tangents Law of Tangents (TOA) Tangent of Angle = Opposite Adjacent See page 19 Tracing Origin of Bloodspots • Point of convergence – 2 dimensional image • Point of origin – adds 3rd dimension to image • In practice: – use of string & protractor at scene – use of computer at laboratory Analyze crime scene pg 21 That’s all folks!