Bloodstain Pattern Analysis

Blood structure

Plasma: 52-62%

White Blood Cells and Platelets: <2%

Red Blood Cells: 38-48%

There is no DNA in mature blood cells

True

White blood cells contain DNA

True

Classifying Bloodstain Patterns

Spatter: occurs when a blood mass is broken up into small droplets and put into free flight by some mechanism. When these droplets strike a surface, they produce circular or elliptical shaped stains

Non-Spatter Stains: Passive and Altered

Spatter, Passive, Altered

Spatter:

• Impact

• Cast-off

• Expiration

• Splash

• Projected

• Forward

• Back

Passive:

• Drip Stain

• Drip Trail

• Drip pattern (liquid into blood)

• Pool

• Flow

• Saturated Stain

Altered:

• Transfer

• Wipe

• Swipe

• Insect

• Void

Data: Shape

Shape of the individual stains

• Circular

• Elliptical

• Pattern

• Irregular

Data: Distribution

Refer to Picture

Drip

A bloodstain resulting from a falling drop that forms due to gravity

Drip Trail

A bloodstain pattern resulting from the movement of a source of drip stains between two points

Drip Pattern

A bloodstain resulting from a liquid that dripped into another liquid, at lead one of which was blood.

Parent Stain – a bloodstain

from which a satellite stain

originated.

Satellite Stain – a smaller

bloodstain that originated

during the formation of the

parent stain as a result of

blood impacting surface or

blood into blood.

Flow

A bloodstain resulting from the movement of a volume of blood on a surface due to gravity or movement of the target surface

Pool

A bloodstain resulting from an accumulation of liquid blood on a surface.

Saturation Stains

A surface bloodstain soaked in liquid blood on a surface

Expiration Pattern

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound.

Projected Blood (arterial spurt)

A bloodstain pattern resulting from the ejection of blood under hydraulic pressure, typically from a breach in the circulatory system

Splash Pattern

A bloodstain pattern created from a large volume of liquid blood falling onto a surface

Cast-off

A bloodstain pattern resulting from blood drops released from an object due to its

motion.

Cessation Pattern

A bloodstain pattern resulting from blood drops released from an object due to its

abrupt deceleration.

Transfer

A bloodstain resulting from contact between a blood-bearing surface and another surface

Swipe

A bloodstain resulting from the transfer of blood from a blood- bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces

Wipe

An altered stain resulting from an object moving through a pre-existing wet bloodstain.

Insect Stain

A bloodstain resulting from insect activity. It can mimic impact spatter, however no logic or overall pattern to it.

Void

An absence of blood in an otherwise continuous bloodstain or bloodstain pattern

Area of Convergence

• By considering the directionality of a

number of stains in a pattern, the CSI

can visualize the general area from

which the droplets originated.

• The reverse vectors defined by the

individual stains; directionality may (if

the stains are related) converge in the

scene.

• This convergence in a two-dimensional

area referred to as the pattern’s

convergence area (point)

Area of Origin

• Considered together the impact and

directional angles for a number of stains

associated with an impact event (a point

source dispersion of blood) may define

the origin of the stains in three

dimensions.

• Typically 10-15 individual stains are

selected in order to determine the area

of origin.