Blood Spatter Analysis

1. Blood Spatter Analysis

2. General Info gained from bloodstain pattern analysis: • 1. the direction the blood originated from • 2.the angle that the blood drop struck a surface • 3. location/position of a bleeding individual at a crime scene • 4. min # of blows that struck a bleeding victim • 5. approx location of a person delivering impact/injury • 6. movement of a bleeding person at the scene

3. Activities to verify BSA interpretation: Measuring and reconstruction

4. Surface Tension and Surface Texture • Blood is mostly water: has surface tension • The harder / smoother / nonporous the surface, the less spatter there is (tile) • The rougher / more absorbent a surface is, the more spatter there is (carpet, wood, bed) • The rougher surface breaks up the surface tension of the blood, which cause more spatter.

5. Satellite spatter: small drops of blood around the edges of a drop or pool of blood. Results from blood hitting a surface.s Notice spines

6. 20° 30° 50° 40° 80° 60° 70° 90° 10° 14 Angle of Impact Gravitational dense zone at lower edge Adapted from Introduction to Forensic Sciences, W. Eckert, CRC, 1997

7. Direction and Angle of Impact • Shape of blood stain can help us tell direction of travel • The more elliptical the shape, the greater the angle of impact, the longer the tail, the faster the blood was traveling. Angle of impact: angle formed between path of bld drop and the surface it hits.

8. FORMULA: sin A = width of blood stain length of bld stain + / - 5 degrees

9. IMPACT SPATTER • Bld stain pattern produced when an object makes forceful contact with a source of blood • Forward spatter: outward and away from the source of the bld • Backward spatter: (blowback) backward from the source • Classification of impact spatter: based on the velocity of the blood droplet (speed) • Force / velocity / increase / decrease

10. Bullet enters foam bullet exits foam bullet 59 Gunshot: back& forward spatter Bloodstained foam held just above target surface. Bullet passing L to R just above sheet Back-spatter on entry Forward spatter on exit

11. Back spatter on steadying hand

12. Classifying Impact Spatter • LOW VELOCITY IMPACT SPATTER (LVIS) • Drop moving less than 5 ft/sec • Diameter of drop is 3mm or more • Dripping bld, cast off, splashing, arterial spurting • MEDIUM VELOCITY IMPACT SPATTER (MVIS) • Diameter of 1-3 mm • Moving 5-25 ft/sec • Blunt force truama • HIGH VELOCITY IMPACT SPATTER (HVIS) • Diameter less than 1 mm, looks like a fine mist • Moving 100 ft/sec or more • Gunshots or explosions

14. LVIS

15. MVIS

16. HVIS

17. 65 Forward spatter (closer view)

18. Origin of Impact Patterns • Origin of impact: where the blood came from; source / position of victim, weapon, etc… • Area of convergence: 2D place (on the ground) where the blood originated from • Determined by drawing straight lines thru the longitudinal axis of several blood stains. • Area of origin: 3D place where blood came from • Use angle of impact and area of convergence

19. Stringing Method • 1. find area of convergence and angle of impact. • 2. place pole/stand as an axis on the area of convergence. • 3. attach string to end of droplet and use protractor to lift string to correct angle. Tie string to pole/Stand, maintaining proper angle. • 4. View area and attach all strings.

22. Gunshot spatter • Guns: forward and back spatter • Very fine drops, mist-like spray • Drawback effect: when blood (back spatter) enters the barrel of a gun

23. Cast off • Bld covered object flings bld onto surface(s) • Bloody fist • Repeated blows by weapon • Infer type object: width of pattern, size of drops related to size of object bld came from • Min #: each blow marked by upward (and downward arc pattern (or forward and backward) • At least 2 hits- 1 to break skin, 2nd to pick up bld

25. 24 Downswing of Hammer

26. 25 Cast-off from Weapon ceiling

27. 26 Overhead swing with bloodied metal bar

28. 27 Cast-off Pattern (1/2)

29. 28 Cast off Pattern (2/2) 1 2 3

30. 29 Cast off Pattern (2/2) ? Sequence

31. 30 Cast off Pattern (2/2) ? Sequence 1 (4 spots) 2 (3 spots) 3 (2 spots) If weapon does not pick up more blood, spatter from subsequent backswings becomes progressively less. In practice weapon picks up more blood with each successful blow.

32. 31 Three overhead swings with hatchet

33. Arterial Spray • Spatter pattern created from a main artery injury- usually carotid in neck • Bld spurts with heart beat • Knife wound, stabbing Direction: vertical arc shows movement, lg stain at end of pattern

34. 53 Neck incisions ‘Hesitation’ injuries Probe in carotid artery Thyroid cartilage

35. 50 Arterial Spurt Pattern • Blood exiting body under arterial pressure • Large stains with downward flow on vertical surfaces • wave-form of pulsatile flow may be apparent

36. 52 Neck incisions (scene)

37. 51 Small arterial spurt spatter broken pottery

38. 32 Cast-off & medium velocity spatter

39. 33 Cast-off & medium velocity spatter 2

41. Expirated Blood Patterns • Bld expelled from the mouth or nose, under great pressure; • HVIS:very fine spatter • LVIS: drops seen as well • See bubbles! • (Also, can be lighter in color, mixes with saliva)

43. Void Patterns • Pattern created when an object / person blocks blood from hitting a surface • Important: bc it means something / someone is missing from the crime scene

45. Contact / Transfer Patterns • Transfer pattern: pattern when a bloody surface comes into contact with another surface. • Removed without movement • Fingerprints, shoeprint, footwear, tool print, fabric all can leave transfer patterns • SWIPE pattern: like transfer, but movement occurs; will “feather”

47. 49 Blood pool (10 drops) after stamping Stamp 2

48. Transfer from hair (hair-swipe) 1 69

49. Transfer from hair (hair-swipe) 2 70