Bloodstain Pattern Analysis

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Bloodstain Pattern Analysis
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Summary

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

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What is Blood?
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Introduction to Blood
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Blood Spatter (or splatter)

• Blood drops form different shapes and sizes

Blood spatter analysis uses the shapes and sizes
to reconstruct the crime scene.
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Blood Spatter gt Distance

• Determining Distance Blood Falls

Blood drops fall as small spheres
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Blood Spatter gt Distance

• Determining Distance Blood Falls

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

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Blood Spatter gt Distance

• 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
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Blood Spatter gt Distance

• Determining Distance Blood Falls

However, size of drop also depends on the volume
of the drop.
Volume depends on the object blood originated
from (needle small bat large).
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Blood Spatter gt Distance

• Determining Distance Blood Falls

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

• Effect of Surface

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

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Blood Spatter gt Direction

• Determining Direction of Blood

Narrow end of a blood drop will point in the
direction of travel.
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Blood Spatter gt Direction

• Determining Direction of Blood

If more than one drop (from spatter) results, the
point of origin can be determined
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Blood Spatter gt Direction

• Determining Direction of Blood

If more than one drop (from spatter) results, the
point of origin can be determined
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Blood Spatter gt Direction

• Determining Direction of Blood

This is a 2-dimensional point of origin. It is
possible to determine the 3-D point of origin
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Blood Spatter gt Direction

• 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)

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Blood Spatter gt Direction

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

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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

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Blood Spatter

• Spattered Blood can

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

• Help determine the mechanism which created the
  pattern.

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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
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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.

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Blood Spatter

• Gunshot Spatter

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

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Blood Spatter

• Types of Spatter

Castoff Pattern Blood flung off of swinging
object.
Can reconstruct where assailant and victim were
positioned.
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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.

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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.