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Bloodstain Pattern
Analysis
Dr Rizwan Zafar . MBBS, DMJ
Lecturer, Forensic Medicine
Deptt CMH Lahore Medical
College.
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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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Determining Distance Blood Falls
Blood drops fall as small spheres
Blood Spatter > Distance
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Determining Distance Blood Falls
Drops form circle when hitting surface
Size depends on speed of blood drop
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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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Determining Distance Blood FallsHowever, 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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Determining Distance Blood Falls
Since the volume of blood is unknown
The distance a drop has fallen
cannot be measured.
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Effect of Surface
Smooth surface = smooth sphere
Rough surface may cause some splatter
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Determining Direction of Blood
Narrow end of a blood drop will point in the
direction of travel.
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Determining Direction of Blood
If more than one drop (from spatter) results,
the point of origin can be determined
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Determining Direction of Blood
If more than one drop (from spatter) results,
the point of origin can be determined
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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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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 tosurface; Direction
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For each blood
drop, a string can
be guided back tothe point of origin.
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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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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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Spattered Blood
In general, for higher impacts, the pattern is
more spread out and the individual stainsare smaller.
Low impact = beating
High impact = gunshot
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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 agunshot.
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Gunshot Spatter
Gunshots result in back spatter
(where bullet enters) and forward
spatter (where bullet exits).
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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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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 cancreate a spatter.
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Types of Spatter
Castoff Pattern = Blood flung off of
swinging object.
Can reconstruct where assailant and victim
were positioned.
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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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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.
Blood Spatter
