Blood Spatter Analysis Blood Spatter not splatter is

Blood Spatter Analysis

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?

Simpson Crime Scene

Is blood spatter evidence consistent with the story told by witness or suspect?

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

Blood dropped from different heights

Types of Blood Spatter • Passive • Transferred • Projected • Cast off dripped blood hand print artery bleed from a weapon

Transferred blood Footprint Handprint

Projected blood Arterial gush on wall

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

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 • Blood animations

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 60 80 50 a 70 40 l l Floor 30 20 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

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 3 rd 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!