1. Bloodstain Pattern Analysis
Crime Scene Reconstruction

2. And you think your job is bad

3. Can be done by: Direct scene evaluation
Best done before scene is disturbed
Careful study of scene photos
The photos MUST be properly done

4. Information possible Origin of the stain pattern
Distances between impact & area of origin
Type & direction of impact
Object(s) that produced stain(s)
# of shots or blows
Position of victim, suspect & objects

5. Position of victim

6. Object that produced stain

7. Object that produced stain

8. Position of object

9. Movement & direction of victim, suspect & object after bloodshed
Support or contradict statements
More info for post mortem interval
Correlate with pathology findings (arterial spurt)

10. Movement after bloodshed

11. Characteristics used Number of spots Their location, size and shape
Surface characteristics where stain is deposited

12. Stain size and shape
The tapered end of the drop will point in the direction of travel

13. Surface Tension A “skin” is formed around the blood drop
This causes the surface area of the drop to minimize
The drop is spherical – NOT tear drop shaped as they are often shown

14. Surface tension
The drop will oscillate early during the flight but that is quickly damped because of the drop’s viscosity

15. Average volume of a blood drop
There is no average volume of a blood drop
Some literature will suggest a volume of .05 ml.
The drop volume is directly related to the surface texture from where the blood drops

16. A different sized drop will form from a machete than will form on the end of a screwdriver

17. Terminal velocity The maximum speed the blood drop can reach
The acceleration rate is offset by air resistance

18. The larger the droplet the less the effect and the smaller the droplet the greater the effect
There will be more smaller drops but they will not travel as much distance

19. Shape of spot
Surface texture is CRITICAL when evaluating the shape of the spot
A smooth, hard, non-porous surface will result in less spatter – generally
A porous or irregular surface usually results in more spatter

20. Surface texture
The surface texture may vary considerably even if the material is the same

21. Horizontal motion
Directionality can be determined from the stain shape & edge characteristics
A tapered or scalloped edge indicates the direction of travel

24. Horizontal motion & impact angle
The greater the horizontal motion (faster) or the lower the impact angle – the more elongated the stain will appear

25. Horizontal motion & impact angle
As the impact angle gets closer to 90° - the “teardrop” pattern is less obvious and the leading edge is determined by small edge scallops

26. Impact angle & origin
Origin can be determined in two dimensions by drawing lines through the individual blood drops along their direction of travel
The actual spatter occurred at some point above this 2-D convergence

27. Impact angle
By calculating the impact angle of drops within the stain we can add the third dimension of height
This is extremely useful for repositioning a victim- prone, kneeling, standing

28. Impact angle
We are determining the internal angle – the bloodshed occurred within that angle
It is impossible for the bloodshed to have occurred outside of that angle

29. Impact angle
By measuring the width and the length of the stain in millimeters – we can calculate the impact angle

30. Measurement of the stain
The stain is measured as an ellipse – a closed curve in the form of a symmetrical oval
Be careful measuring the stain
Especially as the stains get closer to 90°

31. To measure a stain Find the widest point of the stain
Measure across at that point (mm)
From that point measure to the top of the stain (mm)
Double the measurement you’ve made to the top

32. To calculate impact angle
Width in millimeters
Length in millimeters
Width ÷ Length = .something
Find the closest # to .something on the sine table

33. Impact angle & sine table
Example
Width = 15 mm
Length = 30 mm
15÷30 = .50
.50 = 30 degrees on the sine table
The stain has an impact angle of 30°

35. Dripped blood
A primary pattern area and small droplets around that area
The droplets will not “rebound” high off the impact surface

36. Dripped blood

37. Dripped blood – victim standing still

39. Arterial Spurt

41. Dripped blood

48. Cast off blood Smaller droplets Spot size is nearly uniform
More of a linear pattern – but not always a straight line
Can calculate impact angle to reposition attacker

49. Spatter evidence - generally
Most of the blood will go in the direction of force
A lesser amount will come back toward the force
Always check those involved for back spatter

50. Spatter evidence - generally
Look for where the blood is…and where the blood isn’t
Do you find blood where you would expect to find it?
Back spatter will be limited to about 3 feet
Spatter found on a suspect puts them in proximity when the blood was shed

51. Medium force spatter Small droplets – about 1/8th inch or smaller
Impact speed of about 5-25 feet per second
Consistent with an attack involving a fist, axe, knife, club etc.
Consider surface texture

52. High force spatter Mist-like pattern Like an aerosol spray
Do not travel more then 3-4 feet
All gunshots, machinery accidents

53. High force spatter Back spatter – will depend upon: Weapon Ammo
Target distance
Clothing
Location of wound

54. High force spatter Always check the cuff, sleeve, watch, ring etc.
Check the inside of the pants pocket

55. High force back spatter
Will only travel about 3 feet – at best
A second shot (into a bloodied area) will increase back spatter

56. High force – 6 inches in front

57. High force – 6 inches in back

58. High force – 12 inches in front

59. High force – 12 inches behind

60. A day many waited for