bloodstain pattern analysis
DESCRIPTION
Bloodstain Pattern Analysis. Summary. What is Blood? Determining Distance of Blood Determining Direction of Blood Types of Blood Stain Patterns. What is Blood?. It is a tissue Blood Volume 5 to 6 liters in adult males 4 to 5 liters in adult females A 40% blood volume loss* = death - PowerPoint PPT PresentationTRANSCRIPT
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Bloodstain Pattern Analysis
![Page 2: Bloodstain Pattern Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062323/568161e7550346895dd20f63/html5/thumbnails/2.jpg)
Summary
What is Blood? Determining Distance of Blood Determining Direction of Blood Types of Blood Stain Patterns
![Page 3: Bloodstain Pattern Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062323/568161e7550346895dd20f63/html5/thumbnails/3.jpg)
What is Blood?It is a tissueBlood Volume
5 to 6 liters in adult males4 to 5 liters in adult females
A 40% blood volume loss* = deathLoss of 1.5 L causes incapacitation
* Internally or externally
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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
Blood Spatter > Distance
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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
Blood Spatter > Distance
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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).
Blood Spatter > Distance
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Determining Distance Blood Falls
Since the volume of blood is unknown…
The distance a drop has fallen cannot be measured.
Blood Spatter > Distance
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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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Determining Direction of Blood
If more than one drop (from spatter) results, the point of origin can be determined
Blood Spatter > Direction
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Determining Direction of Blood
If more than one drop (from spatter) results, the point of origin can be determined
Blood Spatter > Direction
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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
Blood Spatter > Direction
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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 to surface; <10 at a sharp angle)
Blood Spatter > Direction
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For each blood drop, a string can be guided back to the point of origin.
Blood Spatter > Direction
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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 stains are 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 a
gunshot.
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 doesn’t 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 can create 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