Bloodstain Pattern Analysis

1
Bloodstain Pattern Analysis

• Dr. Jason Linville
• UAB Spring 2005
• jglinvil_at_uab.edu

2
Summary

• What is Blood?
• Determining Distance of Blood
• Determining Direction of Blood
• Types of Blood Stain Patterns

3
What is Blood?
4
Introduction to Blood
5
Blood Spatter

• Blood drops form different shapes and sizes

• Blood spatter analysis uses the shapes and sizes
  to reconstruct the crime scene.

6
Blood Spatter

• Determining Distance Blood Falls

• Blood drops fall as small spheres

7
Blood Spatter

• Determining Distance Blood Falls

• Drops form circle when hitting surface
• Size depends on speed of blood drop

8
Blood Spatter

• Determining Distance Blood Falls

• Faster drop larger diameter (size)
• Higher distance larger diameter

• Due to air resistance, speed maxes out at
  distances above about 7 feet

9
Blood Spatter

• Determining Distance Blood Falls

• However, size of drop also depends on the volume
  of the drop.

• Volume depends on object blood originated from
  (needle small bat large)

10
Blood Spatter

• Determining Distance Blood Falls

Since the volume of blood in a drop is unknown
The distance a drop has fallen cannot be measured.
11
Blood Spatter

• Effect of Surface

• Smooth surface smooth sphere
• Rough/porous surface may cause some splatter

12
Blood Spatter

• Determining Direction of Blood

• Narrow end of a blood drop will point in the
  direction of travel.

13
Blood Spatter

• Determining Direction of Blood

• If more than one drop (from spatter) results, the
  point of origin can be determined

14
Blood Spatter

• Determining Direction of Blood

• If more than one drop (from spatter) results, the
  point of origin can be determined

15
Blood Spatter

• Determining Direction of Blood

• This is a 2-dimensional point of origin.
• It is possible to determine the 3-D point of
  origin

16
Blood Spatter

• Determining Direction of Blood

• The angle can be determined mathematically.
• Width/Length, then take the inverse sin (sin-1).
• This number is the impact angle (90
  perpendicular to surface lt10 at a sharp angle)

17
Blood Spatter

• For each blood drop, a string can be guided back
  to the point of origin.

18
Blood Spatter

• Types of Spatter

• Spattered Blood random distribution of
  bloodstains that vary in size

• Amount of blood and amount of force affect the
  size of blood spatter.

• Can result from gunshot, stabbing, beating

19
Blood Spatter

• Spattered Blood can

• Help determine the location of the origin of the
  blood source.

• Help determine the mechanism which created the
  pattern.

20
Blood Spatter

• Spattered Blood

• In general, for higher impacts, the pattern is
  more spread out and the individual stains are
  smaller.

• Low impact beating
• High impact gunshot

21
Blood Spatter

• Types of Spatter

• Gunshot Spatter can result in a mist-like
  spatter that indicates a gunshot.

• Not all gunshots will result in misting.

• If misting is present, it is most likely a
  gunshot.

22
Blood Spatter

• Types of Spatter (gunshot)

• Gunshots result in back spatter (where bullet
  enters) and forward spatter (where bullet
  exits).

23
Blood Spatter

• Types of Spatter

• Beating and Stabbing Spatter larger individual
  stains

• First blow usually doesnt result in spatter
  since there is not yet any exposed blood.

24
Blood Spatter

• Types of Spatter

• Satellite Spatter Free falling drops of blood
  that fall onto a spatter pattern.

• These drips are usually much larger than impact
  spatter.

• However, blood dripping into blood can create a
  spatter.

25
Blood Spatter

• Types of Spatter

• Castoff Pattern Blood flung off of swinging
  object.

• Can reconstruct where assailant and victim were
  positioned.

26
Blood Spatter

• Types of Spatter

• Expirated Bloodstain Pattern Blood can
  accumulate in lungs, sinuses, and airway.
  Forcibly exhaled.

• Can appear like beating or gunshot pattern.

• May be mixed with saliva or nasal secretions.

27
Blood Spatter

• Alteration of bloodstain over time

• Blood dries and clots over time.
• Difficult to estimate the time the blood exited
  the body.
• Clotted smears can indicate time of movement