Bloodstain Pattern Interpretation Forensic Science

Bloodstain Pattern 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). Forensic Science Blood 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. Forensic Science Blood 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. Forensic Science Blood 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. Forensic Science Blood Facts - History

1971 – Herbert MacDonell - Published Dept of Justice booklet titled: “Flight Characteristics and Stain Patterns of Human Blood” Forensic Science Blood 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. Forensic Science Blood Facts

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

What Is “Spatter”? - Blood which has been dispersed as a result of force applied to a source of blood. ( Not “Splatter” ) Forensic Science Blood Facts

What Are “Spines”? - The pointed edges of a stain which radiate away from the central area to form the spatter. Forensic Science Blood Facts

What Is “Back Spatter”? - Blood directed back towards the source of energy or force that caused the spatter. Forensic Science Blood Facts

And “Forward Spatter”? - Blood which travels in the same direction as the force which caused the spatter. Forensic Science Blood Facts

And A “Parent Drop”? - A drop of blood from which a cast-off or satellite spatter originates. Forensic Science Blood Facts

Satellite Spatter? - Small droplets that break off from the parent spatter upon impact with a target surface. Forensic Science Blood Facts

Cast-Off Stain? – Blood that has been thrown from an object (ex: weapon) onto a target other than the impact site. Forensic Science Blood Facts

The Impact Site? – Usually the point on the body that received the blow / force and from which the blood was shed. Forensic Science Blood Facts

The “Flight Path”? - The path of the blood drop, as it moves through space, from the impact site to the target. Forensic Science Blood Facts

What Is A “Void”? - An absence of stains in an otherwise continuous bloodstain pattern. Forensic Science Blood Facts

What is this? Forensic Science Blood 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. Forensic Science Blood Facts

What is this? Forensic Science Blood Facts

Angle of Impact (answer) - The acute angle formed between the direction of a blood drop and the plane of the target surface. Forensic Science Blood Facts

Forensic Science Blood Facts

What is this? (red circle) Forensic Science Blood Facts

Point of Convergence - Common point in a 2 dimensional space to which the trajectories of several drops can be retraced. Forensic Science Blood Facts

What is this? Forensic Science Blood Facts

Point of Origin - Common point in a 3 dimensional space to which the trajectories of several drops can be retraced. Forensic Science Blood Facts

Direction of Flight? - The trajectory of a blood drop which can be established by its angle of impact and directionality angle. Forensic Science Blood Facts

A “Passive Drop”? - (Bleeding) Bloodstain drop(s) created or formed by the force of gravity acting alone. Forensic Science Blood Facts

Passive Drop Spatters Forensic Science Blood Facts

What Is “Misting”? - Blood which has been reduced to a fine spray, as a result of the energy or force applied to it. Forensic Science Blood Facts

Projected Blood? - Blood under pressure that strikes a target. ex: Expirated Blood Forensic Science Blood 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. Forensic Science Blood Facts

What Is This? Forensic Science Blood Facts

A “Transfer Pattern” Forensic Science Blood Facts

What is this? Forensic Science Blood Facts

Forensic Science Blood Facts A “Wipe” (answer) – pattern created when a secondary target moves through an existing wet blood stain.

What is this? Forensic Science Blood Facts

Swipe (answer) – The transfer of blood onto a target surface by a bloody object that is usually moving laterally. Forensic Science Blood Facts

THE END Forensic Science Blood Facts