Blood Spatter

Video - Blood Spatter 101

Video clip - Dexter, "It's spatter not splatter!"

Blood Spatter Evidence

Crime scene investigators look for:

–Origin of blood

–Type of instrument that caused bloodstains

–Direction from which an object struck the

victim

–Location & movement of victim

–Distribution of blood stain (spatter)

–Appearance of blood (dried/fresh)

Video - Dexter Blood Spatter

Investigating SpatterHerbert L. MacDonell studied blood

spatter and suggested investigators note

the following:

1. Texture of surface

will affect spatter

pattern

(The more

textured: wood,

concrete – the

more spatter)Video - How Surface Texture Affects

Bloodstain Patterns

Investigating Spatter2. Pointed end of blood stain shows the

direction blood was traveling

Investigating Spatter Cont.

3. Impact angle:

90o – more circular blood stain

< 90o – more elongated blood stain

Video - How Impact Angle Affects Bloodstain Elongation

Investigating Spatter Cont.4. Origin of blood can be determined from

convergence of lines from points

Investigating Spatter Cont.

5. Velocity of blood spatter:

– Low velocity – due to gravity

Investigating Spatter Cont.

– Medium velocity – from blunt objects or

expirated blood

Investigating Spatter Cont.– High velocity – mist-like, usually result of

a bullet

Collection of Blood Evidence

All human evidence (blood, semen, saliva, etc) must be packaged in paper (plastic can cause mold destruction of DNA)

Samples must be refrigerated

Each piece of evidence must be packaged separately

Label all containers with name, date, & sample location

Do not fold clothing

Blood Spatter Patterns

Elongated Drops -

Movement

Cast Off Void in Spatter

Contact Stain Small Spots –

High Velocity

Large Spots –

Low Velocity

Match the correct pattern with each

description:

The blood was traveling at a relatively fast

rate (more force equals smaller spatter).

Small Spots – High Velocity

Victim was moving, their speed is relative to the

amount the spots are stretched and how far

they are spaced apart (also indicates

directionality)

Elongated Drops - Movement

The blood was traveling relatively slowly

Large spots – low velocity

Straight, elongated lines of spatter indicate that

blood was thrown by a moving object in a

change of direction (can show how many times

a victim was struck)

Cast off

Something blocked the blood spray

Void

Large stain on a surface caused by contact with

a bloody object

Contact stain