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Chapter Ten – Bloodstain Pattern Analysis

Chapter Ten – Bloodstain Pattern Analysis. FRSC 8104 Criminalistics II Professor Bensley. FRSC 8104 – Bloodstain Pattern Objectives. Discuss the information that can be gained from bloodstain pattern analysis about the events involved in a crime.

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Chapter Ten – Bloodstain Pattern Analysis

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  1. Chapter Ten – Bloodstain Pattern Analysis FRSC 8104 Criminalistics II Professor Bensley

  2. FRSC 8104 – Bloodstain Pattern Objectives • Discuss the information that can be gained from bloodstain pattern analysis about the events involved in a crime. • Explain how surface texture, directionality, and angle of impact affect the shape of individual bloodstains. • Calculate the angle of impact of a bloodstain using its dimensions. • Describe the classifications of low-, medium-, and high-velocity impact spatter and appreciate how those classifications should be used. • Discuss the methods to determine the area of convergence and area of origin for impact spatter patterns. • Understand how various blood pattern types are created and which features of each pattern can be used to aid in reconstructing events at a crime scene. • Describe the methods for documenting bloodstain patterns at a crime scene.

  3. FRSC 8104 – Blood Spatter Outline • Introduction • What is it? • What can we learn from interpretations? • Properties of Blood • Basic Properties • Shape of Drops • Surface Tension Way Cool Videos!

  4. FRSC 8104 – Blood Spatter Outline • Volume of blood drops • Diameter of Stain vs. Distance Fallen • Maximum Terminal Velocity Videos 1 and 2 A high-speed photograph time series comparing the impact dynamics of three different droplet diameters. Impact velocity was 4.2 m/s and the surface was paper. http://www.hartnell.cc.ca.us/faculty/jhughey/Files/bloodstainshapes.pdf

  5. FRSC 8104 – Blood Spatter Outline • Bloodstain Formation and Impact Angle • Direction of Travel • Angle of Impact Determinations • We love Trigonometry! Videos – 80 degrees (Top View) 80 degrees (Side View) 20 degrees (Top View) 20 degrees (Side View)

  6. Angle of Impact

  7. Angle of Impact SIN < = Width  (a) 1.5cm               Length (c) 3.0cm Width  (a) 1.5cm = SIN < Length (c) 3.0cm 0.5 = SIN < < = 30 degrees

  8. FRSC 8104 – Blood Spatter Outline • Locating the Source of Bloodstains • Point (AREA) of convergence Video of Rat Trap at less than a 5 degree angle for Point of Convergence http://www.fbi.gov/publications/leb/2005/feb2005/feb2005_img_31.jpg

  9. FRSC 8104 – Blood Spatter Outline • Point (AREA) of origin • Stringing Method • Trigonometry • Graph Paper • Computer (BPA Software) • Limitations • Assume straight lines of travel • Surfaces other than horizontal

  10. FRSC 8104 – Blood Spatter Outline • Altering a Drop of Blood • Changes in volume or changes in shape of resultant pattern • What are goals of BPA? • Various target surfaces • Texture • Thickness • Absorbency • Hardness

  11. Blood Striking Various Surfaces Smooth, Non-Porous Surface (Glass) Linoleum Cement Board Videos of Surfaces – Cotton, Wood, Cement

  12. FRSC 8104 – Blood Spatter Outline • Forces Acting upon Blood • Low velocity impact spatter • Blood dripping into blood • Splashed blood • Gravitational pull up to5 feet/sec. • Relatively large stains4mm in size and greater Videos: #1 #2

  13. FRSC 8104 – Blood Spatter Outline • Medium velocity impact spatter • Beating or stabbing • Force of 5 to 25 feet/sec. • Preponderant stain size1 to 4mm in size Videos: #1 #2

  14. FRSC 8104 – Blood Spatter Outline • High velocity impact spatter • Gunshots, Explosions, Mechanical Accidents • Force of 100 feet/sec. andgreater • Preponderant stain size1mm in size and smaller • Mist like appearance Videos: #1 #2

  15. FRSC 8104 – Blood Spatter Outline • Back spatter vs. Forward spatter

  16. FRSC 8104 – Blood Spatter Outline • Projected Blood Pattern • Running in, stamping in, or slapping a pool of blood • Beating a head on the floor • Arterial gushing or spurting

  17. FRSC 8104 – Blood Spatter Outline • Cast Off Blood Patterns • Blood being cast from a bloody object in motion onto a target surface • Swinging a bloody hand or weapon • Minimum number of blows delivered • Technically not spatter Videos: #1 #2 #3

  18. FRSC 8104 – Blood Spatter Outline • Other Patterns • Transfers

  19. FRSC 8104 – Blood Spatter Outline • Void Patterns

  20. FRSC 8104 – Blood Spatter Outline • Sequence of Events • Swipes vs. Wipes Feathering Indicates Direction of Travel of Swipe Video of Swiping Fingers

  21. FRSC 8104 – Blood Spatter Outline • Time-Lapse Drying • Skeletonizing

  22. FRSC 8104 – Blood Spatter Outline • Time-Lapse Clotting (Serum Stains) http://www.softchalk.com/lessonchallenge/lesson/ImmuneSystems/index.html

  23. FRSC 8104 – Blood Spatter Outline • Diluted Stains • Expiratory Blood • Sneezes, Coughs, Gurgles, Sucking chest wounds, etc. • Skipping Patterns Videos: #1, #2, #3

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