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Blood Spatter
distortion than glass but less than concrete or brick. Image 6 is a spatter
that resulted from blood dropping from about five feet (1.5 meters) directly
down onto a linoleum floor. Look at the edges of the droplet. They have
been slightly distorted by the impact with the nonporous floor.
It can be difficult to determine which direction a spatter came from
when blood falls on some surfaces. For example, droplets tend to splash
less predictably when they fall on surfaces with inconsistencies, such as
rough cut wood. An analysis is still possible, just more time consuming.
Sometimes an expert will take a sample of the surface and do several test re-
enactments of spilling blood. Information gathered in this way can usually
help the scientist decipher the patterns. Image 7 is a typical spatter mark
on a nonporous surface. Notice the irregularity of the edges and
satellite
spatters.
Energy Matters:
High-, Medium-,
and Low-Energy Spatters
The amount of energy used to spatter blood makes a big difference in
the appearance of individual spatter marks. In the interest of gathering
as much information as possible, determining the approximate amount of
energy falls under the tasks of the forensic physicist. Courts usually allow
testimony relating to the amount of energy behind an attack as evidence of
the intent of the attacker. Accidental attacks are not often very hard impacts.
There are three categories of impact energy: high, medium, and low.
Each has a different effect on the size and shape of blood droplets. In
general, as the energy of the impact increases, the size of individual drop-
