Blood Spatter Analysis Familiarization Training for the Scene Investigator Advanced Skills...

Blood Spatter Analysis Blood Spatter Analysis

Familiarization Training for the Scene Investigator

Advanced Skills Investigative Branch 20 February 2008

What can blood stains tell us? What can blood stains tell us?

• Time of the crime

• Sequence of events

• Mechanism of injury

• Locations of persons and things

• Position of victims

• Corroborate testimony


The Investigator’s Role The Investigator’s Role

• Must have a basic understanding of the significance of bloodstain patterns

– Initial evaluation

– Proper documentation

– Preservation of evidence


Physical Considerations of Physical Considerations of Liquid Blood Liquid Blood


Stain Considerations Stain Considerations

• Surface Tension

• Viscosity

• Gravity (or gravitational attraction)

• Velocity

• Surface on which it lands


Velocity Characteristics Velocity Characteristics

• Low

– Free-falling drops

• Medium

– Blunt force ejection

•High – Firearm/Explosion


Mechanisms of Deposition Mechanisms of Deposition • Passive

– Clot, drip, flow, pool, saturation, serum separation

•Transfer – Swipes and wipes

•Projected – Arterial spurts, cast-off, expiratory, splashes

• Miscellaneous

– Fly spots, voids, and skeletonized Advanced Skills Investigative Branch 20 February 2008

Documentation Documentation

• Notes

• Sketches

• Measurements

• Photography

– Photos used in interpretation Must be Normal to Surface

– Include Scales in all shots


Interpretation Rules Interpretation Rules

• Impact vs Transfer on Textured Surfaces

•Age

–Clotting

–Drying

–Color


Calculations and Interpretations Calculations and Interpretations

Path of Blood Drop

L

= Impact Angle L = Length of Stain W = Width of Stain

= arc sin (W/L)


Summary Summary

• What a stain can tell me?

• Investigator’s role

• Characteristics of liquid blood

• Mechanisms of deposition

• Documentation

• Calculation and Interpretation


Blood Spatter Analysis Familiarization Training for the Scene Investigator Advanced Skills...

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