Blood as Evidence

1. Blood as Evidence

2. Blood Pattern Analysis • The use of physics and math to interpret bloodstain patterns within a forensic setting • May show: • Activity at scene • Number of blows • Position of victim and assailant • Whether death was immediate or delayed • Weapon characteristics

3. History • 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

4. Blood collection • Package in NON-air tight container, such as a paper bag, so that no mold grows—dry blood can still be analyzed

5. Properties of Human Blood • 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

6. Blood . . . • 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

7. Significance of SPATTERED blood . . . • 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,)***

9. Look for Convergence!

10. Real Crime Scene

11. Get Computer Help(Software is available!) Notice the “top view”!

12. Classify spatters (3): • LVIS—low impact velocity impact • Force = up to 5ft/sec • diameter= 4 mm+ • Examples: blood drops into blood and footstep spatters

13. MVIS—medium velocity impact • Force = 5-25 ft/sec • diameter = 1-3 mm • Examples: blood flicked off finger and blunt object used on victim

14. HVIS—high velocity impact • Force = +100 ft • Diameter = < 1mm • Examples: gunshots and propellers

15. Weapon used . . . • 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 1st blow) --type of weapon influences pattern

16. Size, Shape, and Directionality(deals with “flight” of bloodstain) • 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

17. Size, Shape, and Directionality(deals with “flight” of bloodstain) • Impact Angle calculation (for elliptical bloodstains) • 1st find ratio of width to length (see picture) • Then take the arc sin of that ratio • Thus . . . • Angle of impact = sin-1 (width/length)

18. sin θ = W / L W L What does W = L mean? sin θ = 1 → θ = 90 Drop is a circle!

19. Angle of Impact“The tail tells the tale” • 90 degrees – • 60 degrees – • 30 degrees – • 10 degrees –

20. Calculated point of origin • Closer for high velocity spatter or when stains originate closer to where the spatter occurred

21. Rule of Thumb: As impact angle goes down, bloodstain shape becomes more elongated.

22. Cast-off Bloodstains

23. Arterial Gushing

24. String Convergence in a 2 Dimensional Plane Convergence

25. Other Patterns in Blood • 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)

26. Other Bloodstain patterns • 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

27. Other Bloodstain patterns • 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

28. Clotting Time • 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

29. Drying Time • 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

30. Documentation of Bloodstain • 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)