bloodstain pattern interpretation forensic science
TRANSCRIPT
BloodstainPattern Interpretation
ForensicScience
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.
ForensicScienceBlood Facts
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” )
ForensicScienceBlood Facts
What Are “Spines”?
- The pointed edges of a stain which radiate away from the central area to form the spatter.
ForensicScienceBlood Facts
What Is “Back Spatter”?
- Blood directed back towards the source of energy or force that caused the spatter.
ForensicScienceBlood Facts
And “Forward Spatter”?
- Blood which travels in the same direction as the force which caused the spatter.
ForensicScienceBlood Facts
And A “Parent Drop”?
- A drop of blood from which a cast-off or satellite spatter originates.
ForensicScienceBlood Facts
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.
ForensicScienceBlood Facts
The Impact Site?
– Usually the point on the body that received the blow / force and from which the blood was shed.
ForensicScienceBlood Facts
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.
ForensicScienceBlood Facts
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.
ForensicScienceBlood Facts
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.
ForensicScienceBlood Facts
ForensicScienceBlood Facts
Length
WidthArcSineImpact of Angle
What is this? (red circle)
ForensicScienceBlood Facts
Point of Convergence
- Common point in a 2 dimensional space to which the trajectories of several drops can be retraced.
ForensicScienceBlood Facts
What is this?
ForensicScienceBlood Facts
Point of Origin
- Common point in a 3 dimensional space to which the trajectories of several drops can be retraced.
ForensicScienceBlood Facts
Direction of Flight?
- The trajectory of a blood drop which can be established by its angle of impact and directionality angle.
ForensicScienceBlood Facts
A “Passive Drop”?
- (Bleeding) Bloodstain drop(s) created or formed by the force of gravity acting alone.
ForensicScienceBlood Facts
Passive Drop Spatters
ForensicScienceBlood Facts
What Is “Misting”?
- Blood which has been reduced to a fine spray, as a result of the energy or force applied to it.
ForensicScienceBlood Facts
Projected Blood?- Blood under pressure that strikes a target.
ex: Expirated Blood
ForensicScienceBlood Facts
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.
ForensicScienceBlood Facts
What Is This?
ForensicScienceBlood Facts
A “Transfer Pattern”
ForensicScienceBlood Facts
What is this?
ForensicScienceBlood Facts
ForensicScienceBlood Facts
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