Blood Spatter Analysis Blood Spatter Blood drops form

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Blood Spatter Analysis

Blood Spatter Analysis

Blood Spatter Blood drops form different shapes and sizes n Blood spatter analysis uses

Blood Spatter Blood drops form different shapes and sizes n Blood spatter analysis uses the shapes and sizes to reconstruct the crime scene. n

Determining Distance Blood Falls Blood drops fall as small spheres

Determining Distance Blood Falls Blood drops fall as small spheres

Determining Distance Blood Falls Drops form circles when hitting a surface n Size depends

Determining Distance Blood Falls Drops form circles when hitting a surface n Size depends on speed of blood drop n

Faster drop = larger diameter (size) n Higher distance = larger diameter n n

Faster drop = larger diameter (size) n Higher distance = larger diameter n n Terminal Velocity - Due to air resistance, speed maxes out at a certain distance.

n However, size of drop also depends on the volume of the drop. n

n However, size of drop also depends on the volume of the drop. n Volume depends on object blood originated from (needle = small; bat = large)

Since the volume of blood in a drop is unknown… The distance a drop

Since the volume of blood in a drop is unknown… The distance a drop has fallen cannot be measured.

Effect of Surface (Crowning and Satellites) Smooth surface = smooth sphere/circle n Rough/Porous surface

Effect of Surface (Crowning and Satellites) Smooth surface = smooth sphere/circle n Rough/Porous surface may cause some splatter n

Determining Direction of Blood tails n Narrow end of a blood drop will point

Determining Direction of Blood tails n Narrow end of a blood drop will point in the direction of travel.

Determining Direction of Blood n n If more than one drop results, the point

Determining Direction of Blood n n If more than one drop results, the point of origin can be determined This is a 2 -dimensional point of origin. It is possible to determine the 3 -D point of origin

Blood Spatter For each blood drop, a string can be guided back to the

Blood Spatter For each blood drop, a string can be guided back to the point of origin.

Determining Direction and Angle n n n Angle can be determined mathematically. Width/Length, then

Determining Direction and Angle n n n Angle can be determined mathematically. Width/Length, then take the inverse sin (sin-1). This number is the impact angle (90 = perpendicular to surface; <10 at a sharp angle)

n Spattered Blood = random distribution of bloodstains that vary in size Amount of

n Spattered Blood = random distribution of bloodstains that vary in size Amount of blood and amount of force affect the size of blood spatter. n Can result from gunshot, stabbing, beating. n Can determine mechanism that created it (gun, bat, etc. ) n Ex. Low, Medium, High velocity blood spatter n

High Velocity/Impact (gun) - The pattern is spread out and the individual stains are

High Velocity/Impact (gun) - The pattern is spread out and the individual stains are very smaller (misting/aerosol of blood). n Blood forcibly exhaled from airways. n Gunshots also result in back spatter (blowback) and forward spatter (bullet exits). n

Medium Velocity/Impact = A force like beating with bat – larger individual stains. n

Medium Velocity/Impact = A force like beating with bat – larger individual stains. n Often has a trail. (Count blows) n First blow usually doesn’t result in spatter since there is not yet any exposed blood. n

Skeletonized Blood Drops Blood dries and clots over time. n Clotted smears can indicate

Skeletonized Blood Drops Blood dries and clots over time. n Clotted smears can indicate time of movement n

n Wipe – Wet blood is wiped up with something clean like a towel.

n Wipe – Wet blood is wiped up with something clean like a towel. n Swipe – Blood soaked item is run across a non blood soaked surface.