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. Angle of Impact 90° 80° 70° 60° 50° 40° 20° 30° 10° 14
Gravitational dense zone
at lower edge
20°
30°
10°
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. Gunshot: back& forward spatter59
Bloodstained foam held just above target surface.
Bullet passing L to R just above sheet
bullet exits foam
Bullet enters
foam
bullet
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. Forward spatter (closer view)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. Overhead swing with bloodied metal bar26

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

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

30. Cast off Pattern (2/2) ? Sequence29
Cast off Pattern (2/2) ? Sequence

31. Cast off Pattern (2/2) ? Sequence30
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. Three overhead swings with hatchet31

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

35. Arterial Spurt Pattern50
Blood exiting body under arterial pressure
Large stains with downward flow on vertical surfaces
wave-form of pulsatile flow may be apparent

36. Neck incisions (scene)52

37. 51
spatter
Small arterial spurt
broken pottery

38. Cast-off & medium velocity spatter32

39. Cast-off & medium velocity spatter 233

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) 169

49. Transfer from hair (hair-swipe) 270

51. Flow
Flow patterns: patterns created by the movement of blood due to gravity
Look for changes in flow pattern to see if body has been moved.

52. Flow Patterns Blood flows horizontally & vertically71
Flow Patterns
Blood flows horizontally & vertically
Altered by contours, obstacles
Often ends in pool

53. Flow pattern 72

54. 73
Trapped!

55. 76
Blood flow on shirt
Horizontally to R side

56. Pattern on shirt 77

57. Pools Drying time is related to environmental conditions.
Skeletonization: the edges of a drop of bld will dry quickly- usually within 50 sec.
The skeleton will remain even if the blood drop is wiped/swiped.

59. Drip Trail Formed by bld dripping off an object
Can help determine speed and direction of moving object / person.
The more circular the drops are, the slower the person was moving
And look at the direction of the tails…

60. Documentation PHOTOS, PHOTOS, PHOTOS!
Whole scene for overall patterns and orientation
Up-close- with something (like a ruler) for scale.