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Bloodstain Pattern Analysis

Bloodstain Pattern Analysis. The use of physics, math & common sense to interpret bloodstain patterns within a forensic setting. Discoverable from bloodstain pattern interpretation:. Activity at the scene Number of blows Position of victim and/or assailant Death immediate or delayed

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Bloodstain Pattern Analysis

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  1. Bloodstain Pattern Analysis The use of physics, math & common sense to interpret bloodstain patterns within a forensic setting

  2. Discoverable from bloodstain pattern interpretation: • Activity at the scene • Number of blows • Position of victim and/or assailant • Death immediate or delayed • Weapon characteristics

  3. Blood • Fluid travels through a series of tubes in the body (arteries, veins, capillaries, etc…) • Transports oxygen and nutrients to cells • Carries carbon dioxide and wastes away from cells • Helps stabilize internal pH • Carries infection-fighting cells • Helps equalize temperature

  4. What’s in Blood? Plasma portion (50-60% of total volume) • 91-92% water • 7-8% proteins • 1-2% ions, sugars, lipids, amino acids, hormones, vitamins Cellular portion (40-50% of total volume) • White blood cells Neutrophils Lymphocytes Monocytes Eosinophils Basophils • Red blood cells • Platelets

  5. History • 1894-Dr. Eduard Piotrowski, wrote earliest reference to bloodstain pattern analysis • 1939-Dr. Victor Balthazard, first to use physical interpretation of stains • 1955-Dr. Paul Kirk, recognized value of bloodstain interpretation in scene reconstruction. Defense witness in Dr. Sam Sheppard trial. • 1971-Professor Herbert Leon MacDonell promoted bloodstain pattern interpretation as a tool in modern criminalstic labs • 1983-The International Association of Bloodstain Pattern Analysts

  6. Basic Principles: • A free falling drop forms a sphere or ball • A spherical drop will break • when it strikes another object • when acted upon by some force • Surface Texture Affects Spatter Shape

  7. Spatter (NOT Splatter) • is produced by blood being impacted by a force • Spatter size is dependent upon velocity

  8. Low velocity impact spatter • 5 feet per second • spatter 3 mm or greater in diameter • From blood dropping into blood; stepping into blood

  9. Medium velocity impact spatter • 5+ ft per sec to 25+ ft per sec • spatter 3 mm or less in diameter • blunt trauma or sharp trauma • confusion: flicking bloody finger, expiration • check clothing of suspect for spatter

  10. High velocity impact spatter • 100+ feet per second • spatter 1 mm or less in diameter • droplets travel only 3-4 feet horizontally • gunshot trauma; airplane prop; power tools; explosion • confusion: expiration, fly specks difficult to see

  11. Arterial Gushing • Shape = heartbeat

  12. Cast-Off Bloodstains • blood cast from a moving object • occurs with the backstroke during repeated blows or stabs not true spatter • spatter averages 6 mm diameter • blunt or stab (# of trails + 1= min # of blows) • axe or machete (# of trails = min # of blows)

  13. Determining Location of Blood Source • Direction of Travel • Tail of spatter will point in the direction of travel • Angle of Impact • Vertical drop results in circular spatter • Acute angle results in elongated spatter • Measure blood spatter width and length, then calculate the angle it struck the surface • Width/length = sine impact angle • Use inverse sine fxn to calculate angle • Attach string lines to each of these spatters and the lines converge at location of blood source

  14. Transfer Pattern • Produced by a wet, bloody surface contacting a second surface that may result in a portion of a recognizable image (e.g., knife transfer pattern)

  15. Void Pattern • Produced when an object located between the source of the blood and the surface being spattered is removed • negative image of the object

  16. Swipe and Wipe • Swipe -- putting blood onto a surface • Wipe - removing blood from an existing stain • Direction of Travel - feathering always points in the direction of travel

  17. Flow pattern • If there is movement after blood flow, you can see it as a change in the pattern

  18. Drying Time • Drying begins at the periphery and proceeds inward • Drying time is affected by • surface type • amount of blood present • climatic conditions • Skeletonization of Bloodstains • partially dry stains leave a ring that outlines the original spatter • the dryer the stain the less skeletonization shown

  19. Clotting Time • clotting time outside of the body ranges from 3 to 15 minutes • spattered clots indicate that time passed between initial bleeding and later blows coughing of clotted blood may indicate post injury survival time of victim

  20. Discoverable from bloodstain pattern interpretation: • Activity at the scene • Number of blows • Position of victim and/or assailant • Death immediate or delayed • Weapon characteristics

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