Page 4: Hypothesis
Using physics principles (18) it is possible to make predictions about the
final outcome of a moving object. Such predictions are made through the
application of physical principles and mathematical formulas to a given set of
initial conditions. Because historical published information indicates blood
is consistent in its reaction to high velocity forceful impact, the focus of
this experiment is to prove:
Regardless of blood volume, or projectile
caliber and velocity, when a bullet strikes blood, without some interference
such as wound shoring or heavy clothing, some blood will be projected back
toward the source of the impact. The majority of blood will be projected
forward with the direction of travel of the projectile in perforating wounds.
Additionally, we seek to determine if the direction of travel for the
projectile creating the patterns can be determined by comparison of the
patterns created in a single incident.
Collection of Data
Data collection for
the analysis was accomplished by shooting through a variety of samples of whole
human blood (19), at a series of distances (20) and with a wide diversity of
projectile caliber (21).
The series of experiments was completed over 20
times during the past 15 years, the majority of times in a classroom setting as
an instructor in this field.
The bloody target in the large majority of
tests was a bloody sponge. However, plastic bags containing blood soaked
clothing, blood soaked sponges and liquid blood were also used as targets. The
targets were suspended from a stationary frame with wire. This would allow
movement of the targets when impacted upon by the force of the projectile.
Cardboard paper targets were used to capture the resulting disbursed blood
droplets.
On each occasion the experiments were completed in a
prescribed manner. The total number of backspatter and corresponding forward
spatter patterns created and/or examined during this time, number over 1000.
Documentation of Data
If the evidence from an incident is
not documented accurately and appropriately, then it cannot be completely or
properly analyzed. In order to document data and study bloodstain patterns
created as the result of a gun shot injury, a bloody target (usually a sponge)
containing human whole blood was placed in the path of a bullet.
To
document the diameter of the individual stains produced in forward and back
spatter, paper targets were placed vertically before and after the target sponge
at a specific distance. The projectile traveled through a target surface before
striking the bloody sponge, and then traveled through the remaining paper
target. Each caliber weapon was used at each distance. After each individual
experiment, the paper targets were marked with the distance from the bloody
target and caliber of the projectile used to impact the blood. Observations
concerning each set of patterns made in a single shooting incident was made
concerning stain numbers, diameter, shape and distribution. Fragments of sponge
were also noted.
In some instances, videotape was also used to capture
the results of a bullet passing through the bloody sponge.
The projectile
used to create the pattern in the photograph was a Federal .45 caliber 230-grain
bullet traveling at approximately 850 feet per second with 370.65-ft lb kinetic
energy. The bullet was traveling left to right.
Note the multidirectional
travel radiating from the impact site of the projectile in both the forward and
back spatter. The blood will travel in every possible direction not
obstructed.
Assessment of Data
- In every instance during the experimental shooting of bloody targets,
regardless of projectile velocity or blood volume, blood was disbursed back
toward the shooter and propelled forward in the continued direction of travel
of the projectile. This made comparisons of the two patterns created from a
single incident possible.
- Frequently, fragments of the bloody sponge permeated the forward spatter
pattern. Occasionally, sponge fragments were observed in backspatter.
Fragments located in the back spatter were consistently minute in nature;
however, the fragments in the forward spatter varied in size and were
occasionally large.
- Forward spatter traveled farther than back spatter created in the same
incident.
- Forward spatter held a larger volume of blood, expressed as individual
stains, when compared to back spatter created in the same incident.
- On both forward and back spatter targets the stains near the center of the
pattern were circular in shape, as a result of striking the target surface at
or near a 90-degree angle.
- At the perimeters of both forward and back spatter patterns the stains
were more elliptically shaped as a result of the stains striking the target at
an angle.
- The distribution of the droplets was more concentrated when the target
surface was near the bloody target, with the distance between the droplets
increasing as the droplets moved away from the bloody target.
- Increased volume resulted in increased pattern dimensions.
- Forward and back spatter targets displayed a multitude of minuscule blood
droplets, some resembling an atomized spray or mist. The majority of the
stains had an average diameter of .10mm or less.
- In video-captured incidents the target moved dramatically with the
direction of the force (the projectile) upon impact. Normally this larger,
more pronounced movement traveling with the projectile followed a smaller
movement to the front upon impact.
- The videotape used to capture patterns as they were created records 30
frames per second. The video utilized approximately 4-5 frames to capture the
forceful impact pattern when a low velocity, large caliber projectile with a
high KE rate impacted a large volume of blood. This means that particular
pattern was created in its entirety in 1/6 of a second. Some patterns were
created in less than 1/6 of a second.
For an appreciation of
the distribution and dimensions of these stains, the adjacent photograph was
taken through the viewfinder of a special magnifying device. The reference
ruler measures in .02mm increments. The larger stain adjacent to the reference
ruler is .04mm in diameter.
These stains are part of a back spatter
pattern taken at 6 inches. The ammunition used was a Winchester .357 Magnum
SPG, 180 grains, with a velocity of 1180 fps from muzzle, and 556.40-ft lb
kinetic energy.
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