Bloodstain Pattern Interpretation Forensic Science

BloodstainPattern Interpretation

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ForensicScience

BloodstainPattern Interpretation

Equal to 8 % of total body weight

- 5 to 6 liters of blood for males

- 4 to 5 liters of blood for females

- A blood loss of 1.5 liters is required to cause incapacitation.

- A 40 percent blood volume (2 liters) loss is required to produce irreversible shock (death).

ForensicScienceBlood Facts – What Do You Know?

Droplet Characteristics?- Spherical during free fall.- Volume of drop: 0.05 ml.- Terminal velocity: 25.1 ft/sec.- High velocity droplets:

<1 mm diameter.- High velocity droplets:

46 in. maximum distance.

ForensicScienceBlood FactsBlood Facts – What Do You Know?

1514 – London – Richard Hunne- Jailed on 5 counts of heresy.- Found hanged in his jail cell.- Charged with “Self-murder”.- However blood evidence showed Hunne was bleeding BEFORE he was hung.

ForensicScienceBlood Facts - History

1955 – Dr. Sam Sheppard?

Dr. Paul Kirk testified that certain blood evidence on the wall had been “flung” from a bloody object that had been swung in an arc.

ForensicScienceBlood Facts - History

1971 – Herbert MacDonell

- Published Dept of Justice booklet titled:“Flight Characteristics and Stain Patterns of Human Blood”

ForensicScienceBlood Facts - History

What May Blood Evidence Be Able To Disclose?- Source of blood (origin).- Distance blood traveled.- Type of impact & direction.- Number of blows inflicted.- Position of victim during attack.- Position & movement of suspect.

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What Is The “Target”? - The surface upon which blood has been deposited.

ForensicScienceBlood Facts

What Is “Spatter”?

- Blood which has been dispersed as a result of force applied to a source of blood. ( Not “Splatter” )

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What Are “Spines”?

- The pointed edges of a stain which radiate away from the central area to form the spatter.

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What Is “Back Spatter”?

- Blood directed back towards the source of energy or force that caused the spatter.

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And “Forward Spatter”?

- Blood which travels in the same direction as the force which caused the spatter.

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And A “Parent Drop”?

- A drop of blood from which a cast-off or satellite spatter originates.

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Satellite Spatter?

- Small droplets that break off from the parent spatter upon impact with a target surface.

ForensicScienceBlood Facts

Cast-Off Stain?

– Blood that has been thrown from an object (ex: weapon) onto a target other than the impact site.

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The Impact Site?

– Usually the point on the body that received the blow / force and from which the blood was shed.

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The “Flight Path”?

- The path of the blood drop, as it moves through space, from the impact site to the target.

ForensicScienceBlood Facts

What Is A “Void”?

- An absence of stains in an otherwise continuous bloodstain pattern.

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What is this?

ForensicScienceBlood Facts

Target Surface: = the floor

?

Blood Stain

Directionality Angle (answer)

– The direction the blood was traveling when it impacted a target surface. The angle can usually be established from the geometric shape of a stain.

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What is this?

ForensicScienceBlood Facts

Angle of Impact (answer)

- The acute angle formed between the direction of a blood drop and the plane of the target surface.

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Length

WidthArcSineImpact of Angle

What is this? (red circle)

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Point of Convergence

- Common point in a 2 dimensional space to which the trajectories of several drops can be retraced.

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What is this?

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Point of Origin

- Common point in a 3 dimensional space to which the trajectories of several drops can be retraced.

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Direction of Flight?

- The trajectory of a blood drop which can be established by its angle of impact and directionality angle.

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A “Passive Drop”?

- (Bleeding) Bloodstain drop(s) created or formed by the force of gravity acting alone.

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Passive Drop Spatters

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What Is “Misting”?

- Blood which has been reduced to a fine spray, as a result of the energy or force applied to it.

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Projected Blood?- Blood under pressure that strikes a target.

ex: Expirated Blood

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Expirated Blood?

- Blood that is blown out of the nose, mouth or a wound as a result of air flow or air pressure, the propelling force.

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What Is This?

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A “Transfer Pattern”

ForensicScienceBlood Facts

What is this?

ForensicScienceBlood Facts

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A “Wipe” (answer)

– pattern created when a secondary target moves through an existing wet blood stain.

What is this?

ForensicScienceBlood Facts

Swipe (answer)

– The transfer of blood onto a target surface by a bloody object that is usually moving laterally.

ForensicScienceBlood Facts

THE END

ForensicScienceBlood Facts