Transcript Blood Spatter

Blood Spatter
Blood spatter patterns
Help to reconstruct the series of events
surrounding a shooting, stabbing or
beating
 First reference to blood spatter analysis
was in 1894
 Blood spatter evidence was used by the
defense in the Sam Shepard case in 1955
to help exonerate him.

Blood Spatter patterns

Makes it possible to determine:
– the direction the blood was traveling
– the angle of impact
– the point of origin of the blood
– The manner of death, based on blood velocity
Blood drops
Blood is a thick mixture of blood cells and
plasma
 When a person is bleeding, gravity acts on
blood, pulling it downward, making it
longer than it is wide
 Blood is cohesive, so it “sticks together”
and doesn’t separate as it falls
 Blood maintains a round appearance when
it falls on a flat surface

Satellites

Small secondary droplets that have
overcome the force of cohesion and
separated from the main droplet of blood
Six Patterns of Blood Spatter
1.
Circular Drops – produced by blood
falling directly to the floor at a 90 degree
angle
- secondary satellites will be produced if
the surface is textured
- this is known as passive fall
Patterns (continued)
2.
Arterial spurts or gushes found on walls
or ceilings
- caused by the pumping action of the
heart
Patterns (continued)
3.
Splashes – shaped like exclamation
points.
- the shape and position of the spatter
pattern can help locate the position of
the victim at the time of attack
Patterns (continued)
4. Smears – left by a bleeding victim
depositing blood as he or she touches or
brushes against a wall or furniture
Patterns (continued)
5.
Trails – left by a bleeding victim as they
move from one location to another
- droplets could be round or smeared or
even appear as spurts
Patterns (continued)
6. Pools of blood – form around a victim
who is bleeding heavily and remains in
one place
More Patterns 
Fine mist – produced by high velocity
impact, like a gunshot wound
 Low velocity pattern – produced by a
beating with a pipe
 Voids – empty spaces in a spatter pattern
that help determine if something was
moved after the attack

Examination of Directionality of
Blood
The shape of an individual drop of blood can
provide important clues in an investigation.
 As moving blood strikes a surface, several forces
affect the droplet of blood:

– Cohesion – force between two similar substances
– Adhesion – force between two unlike surfaces
– Surface tension – an elastic characteristic along the
outer edge of a liquid casued by the attraction of like
molecules
Lines of Convergence
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
The location from which the blood originated can be
determined if there are at least two blood spatters.
Draw straight lines down the long axis of the blood
spatter and note where the lines intersect – this
indicates the lines of convergence
Crime Scene Investigation of Blood

Even after washing a room of visible
blood, some blood evidence remains

Luminol – causes hemoglobin (the iron
containing portion of the blood) to
fluoresce under black light
Steps in Investigating Blood left at
a Scene
1.
2.
3.
4.
Confirm the stain is blood
Confirm that the blood is human blood
Determine the blood type
Perform a DNA analysis if necessary and
if DNA can be isolated from the sample