- The smaller the size of bloodspatters, the greater the energy
required to produce them. Low, medium, and high velocity impact spatter may be
identified by their respective sizes but exceptions must also one considered.
- Before a drop of blood can fall, absent any other form of
applied energy, gravitational attraction acting on blood must exceed its surface tension.
- Diameter of a large bloodstain will be of little or not value
in estimating the distance a drop of blood has fallen prior to impact.
- When considering the shape of a bloodstain for use in
calculating its angle of impact, only a sharp, well-defined bloodstain should be used for
measuring its width and length.
- Directionality of a blood drop while in flight is usually
obvious from the geometry of its resulting bloodstain. The pointed end indicates the
direction of travel prior to impact on a surface. Directionality may also be
determined when edge scallops appear on only one side of a bloodstain.
- Correct interpretation of bloodstain patterns must include
consideration of the surface texture of the material upon which the bloodstains have been
deposited.
- Surface tension prevents spattering regardless of the
distance a drop of blood has fallen before inpacting a smooth, hard surface such as glass.
- Edge characteristics of a bloodstain have no value in
extablishing the distance a drop of blood may have fallen prior to impacting a surface
unless the nature of the surface texture is considered.
- Conclusions as to the significance of a limited number of
bloodstains should only be drawn with reservations and/or qualifications. It should
be remembered that a few bloodstains do not a pattern make. There is nothing wrong
with admitting that there are insufficient bloodstains available to form an opinion.
It is far better not to have an opinion than to have one that is incorrect.
- When a dozen or more small bloodstains are present in a
recongnizable pattern, their size may allow a prediction as to the energy that was
required to produce them. When the preponderance of individual bloodstain diameters
are less than 1mm, they are consistent with having been produced as a result of a high
velocity impact. Most often they would result from a shooting.
- When the preponderance of dozens of individual bloodstains
are approximately 1mm or more in diamerer, they are consistent with having been produced
as a result of a medium velocity impact. Most often they would result from a beating
or stabbing.
- The shape of a bloodstain is a function of the angle at which
it impacts a surface. Perfectly round bloodstains result from a ninety degree
impact. The angle of impact of an elliptical bloodstain may calculated from its
length to width ratio.
- Bloodstains may often be lifted from the surface upon which
they have been deposited. The harder and smoother the surface the more likely
they may be successfully lifted.
- When measurements and anfles are used to establish the orgin
or origins in space, not only will the actual origin be somewhere below the point or
points of convergence, but it must be remembered that the investigator is determining a
spacial volume and not a small pint of origin.
- Sobriety of the victim will have no significant effect on how
bloodstain patterns are produced. A high blood alcohol level is of no concern to the
interpretation of bloodstain patterns.
- When blood is projected upward with sufficient force to
strike a ceiling, it will almost always be the result of a gunshot having an upward
trajectory. Such a trajectory is more often the result of a suicide rather than it
is a homicide.
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