1 / 20

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

kendall
Télécharger la présentation

Bloodstain Pattern Analysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related