Blood Spatter Analysis

1. Blood Spatter Analysis

2. Bloodstain Pattern Analysis (BPA) • While the use of bloodstains as evidence is not new, the application of modern science has brought it to a higher level. • New technologies (DNA analysis) are available for detectives and criminologists to use in solving crimes and apprehending offenders.

3. Bloodstain Pattern Analysis (BPA) • BPA applies scientific knowledge from other fields to solve practical problems • Draws from biology, chemistry, math and physics • Produces strong, solid evidence

4. BPA can determine • Location and description of individual stains and patterns • Mechanism that created the stains • Direction a blood droplet was traveling • Area of origin • Type of object used in attack • Minimum number of blows • Presence of a subject at a scene • Positioning of the victim, suspect and objects during events • Sequence of events

5. Angle of Impact and Point/Area of Convergence

6. Determining angles of impact • Blood droplets in freefall have the shape of a sphere. • Droplets striking surfaces and leaving well-formed stains make it possible to determine the angle at which the droplet struck the surface.

7. Determining angles of impact • A well-formed stain is in the shape of an ellipse • L/W followed by taking the inverse sin (sin-1) gives the impact angle

8. Point and area of convergence • The point of convergence is the intersection of two different bloodstain paths

9. Point and area of convergence • The area of convergence is the box formed by the intersection of several stains from opposite sides of the impact pattern

11. Point and area of Origin • Point (Area) of Origin – the common point (area) in three dimensional space to which the trajectories of several blood drops can be retraced

12. TARGET SURFACE TEXTURE

13. Target surface texture • Bloodstains can occur on a variety of surfaces, such as carpet, wood, tile, wallpaper, clothing….. • The type of surface the blood strikes affects the amount of resulting spatter, including the size and appearance of the blood drops.

14. Target surface texture • Blood droplets that strike a hard smooth surface, like a piece of glass, will have little or no distortion around the edge.

15. Target surface texture • Blood droplets that strike linoleum flooring take on a slightly different appearance. • Notice scalloping around the edge of the blood droplets.

16. Target surface texture • Surfaces such as wood or concrete are distorted to a larger extent. • Notice the spines and secondary spatter present.

17. BLOODSTAIN PATTERN CATEGORIES

18. Bloodstain pattern categories • Classifies stains based on the mechanism that created them. • Passive bloodstains - created when gravity is the force acting upon it. • Projected bloodstains- occur when some form of energy has been transferred to a blood source • Transfer or contact- produced when an object with blood on it comes in contact with an object or surface that does not have blood on it.

19. PASSIVE BLOODSTAINS

20. Passive Drop A bloodstain drop(s) created or formed by the force of gravity acting alone

21. Drip Pattern A bloodstain pattern that results from blood dripping into blood

22. Flow Pattern A change in the shape and direction of a bloodstain due to the influence of gravity or movement of the object

23. PROJECTED BLOODSTAINS

24. Low Velocity Impact (LVI) Relatively large stains 4 mm in size and greater. Impact velocity up to 5 feet/sec

25. Medium Velocity Impact (MVI) Preponderant stain size 1 to 4 mm size. Impact velocity of 5 to 25 feet/sec.

26. High Velocity Impact (HVI) Preponderant stain size 1 mm in size and smaller. Mist like appearance. Impact velocity of 100 feet/sec and greater.

27. Cast-off Pattern A bloodstain pattern created when blood is released or thrown from a blood-bearing object in motion

28. Arterial Spurting or Gushing Bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery

29. Back spatter – blood directed back towards the source of energy or force that caused the spatter • Expiratory blood – blood that is blown out of the nose, mouth or a wound as a result of air pressure and/or air flow which is the propelling force

30. TRANSFER/CONTACT BLOODSTAINS

31. Swipe Pattern The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered edge.

32. Hair swipe Pattern The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered edge.

33. Wipe Pattern A bloodstain pattern created when an object moves through an existing stain, removing and/or altering its appearance.

34. Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.

35. Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.

36. Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.

37. Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.

38. Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.

39. Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.

40. Sources • BPA Tutorial http://www.bloodspatter.com/BPATutorial.htm • Blood Pattern Analysis (Wikipedia, I kid you not!) http://en.wikipedia.org/wiki/Blood_pattern_analysis_at_crime_scenes • International Association of B. P. Analysts http://www.iabpa.org/