Blood Spatter pattern analysis is used in connection with other physical evidence to determine the sequence of events that occurred within a crime scene to ultimately determine who caused the crime. Much research has been conducted to identify the variables which affect blood pattern formation, but little information is present on the quantitative analysis of cast-off blood spatter patterns as a result of different sized weapons. Cast-off blood spatter patterns are produced when a surface which is saturated with blood is impacted by an implement, moved in a back-ward motion, transferring blood droplets to a secondary surface. The deposited droplets can identify the origin of the assault, the number of swings which occurred, the position of the assailant and whether it was isolated to one area. During this experiment, 14 implements of different length and widths were used to create cast-off blood spatter patterns by being swung at different velocities. The mean droplet areas, width of spatter spread, number of droplets and length of the blood spatter pattern were calculated to determine whether the different weapon variables influence measurements taken. The results showed there was no statistical significant difference between the length and width of the weapon and the blood droplet areas produced. However, there was a strong decrease in the logarithmic droplet area as the velocity of the weapon increased, but the percentage error for this was considerably high. There was a statistical significant difference between the width of the implement and the width of the spatter spread, showing a good accuracy of only 13% error. The observations obtained supports research showing directional tailing and elliptical droplets as the cast-off spatter pattern descends. When observing the length of the spatter both length of the implement and velocity showed a positive increase, but only the velocity had a low percentage error, whereas the length of implement showed close to 100% inaccuracy. The number of droplets produced increased for individual experiments, looking at their repeats, as the velocity increased. However, there was no correlation between the length, width or weight of the implement, counteracting previous research.
Key Words: Blood Spatter Pattern Analysis, Cast-off, Droplet Area, Velocity, Spread.
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