blood spatter patterns murder or self defense?

CHRIS SCHAEFER, OMS I IPRIYA NILESHWAR, OMS INNAEMEKA DIRIBE, OMSI

Blood Spatter Patterns

Murder or Self Defense?

Types of Patterns

High Velocity

Medium Velocity

Low Velocity

How can we find out where the blood came

from?

Pattern Analysis

Select drops of blood with an easily identifiable shape

Measure length and width of droplet

Pattern Analysis

Divide width by lengthThis gives you the sine of the angle at which the blood impacted the wall

Pattern Analysis

Measure angle with protractor and attach a string next to the droplet at angle of impact

Where all the strings come together gives location of source of blood

Which Drops are Good?

Good!

Which Drops are Good?

Bad!

Measure Length and Width

Divide Length by Width

WidthLength

Determining Angle

This will give you a decimal number

The actual formula (for those of you with a little bit of Trigonometry) is arcsin(number)=angle

Math?!? Say What?

Determining Angle

We can just estimate with this table.1 = 6 degree angle

.2 = 11 degree angle

.3 = 17 degree angle

.4 = 24 degree angle

.5 = 30 degree angle

.6 = 37 degree angle

.7 = 45 degree angle

.8 = 53 degree angle

.9 = 64 degree angle1 = 90 degree angle

Measure Angle and String

Area of Convergence

Case

How can we know if a killing was due to self defense or murder?

Story

Stewie states that he was defending himself against Brian who was coming

after him with a knife. Both of them were standing when this happened. Stewie says he struck Brian in the head while he was

still standing.

Evidence

Is he telling the truth?

High or Low Velocity ?

Good or Bad Pattern?

Good Pattern must have a

tail.True/False?