Blood Spattring

8/14/2019 Blood Spattring

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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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Drops form circle when hitting surface

Size depends on speed of blood drop



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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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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

Blood Spatter


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Determining Direction of Blood

Narrow end of a blood drop will point in the

direction of travel.

Blood Spatter > Direction


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If more than one drop (from spatter) results,

the point of origin can be determined



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If more than one drop (from spatter) results,

the point of origin can be determined



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This is a 2-dimensional point of origin.

It is possible to determine the 3-D point of origin



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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

Blood Spatter


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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.

Blood Spatter


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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

Blood Spatter


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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.

Blood Spatter


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Gunshot Spatter

Gunshots result in back spatter

(where bullet enters) and forward

spatter (where bullet exits).

Blood Spatter


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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.

Blood Spatter


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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.

Blood Spatter


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Types of Spatter

Castoff Pattern = Blood flung off of

swinging object.

Can reconstruct where assailant and victim

were positioned.

Blood Spatter


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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.

Blood Spatter


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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

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Blood Spattring