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Blood Stain Patterns

Blood Stain Patterns. Information Obtained: Origin of bloodstains Distance between point of impact and origin Type and direction of impact Object/weapon used Minimum number of blows Position of victim, offender, and objects Movement by victim or offender at scene

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Blood Stain Patterns

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  1. Blood Stain Patterns • Information Obtained: • Origin of bloodstains • Distance between point of impact and origin • Type and direction of impact • Object/weapon used • Minimum number of blows • Position of victim, offender, and objects • Movement by victim or offender at scene • Support/contradict witness statements • Indicate staged/secondary scenes

  2. Blood Stain Patterns • Cast-off Stains

  3. Blood Stain Patterns • Drip patterns

  4. Blood Stain Patterns • Swipe

  5. Blood Stain Patterns • Wipe

  6. Blood Stain Patterns • Effects of Surface Texture • Horizontal drop creates circular pattern • Forces of surface tension • Harder, less porous surfaces- less spatter • Rougher surface = greater distortion (more spatter)

  7. Blood Stain Patterns • Impact Angles • Defined as the internal angle at which blood strikes a target surface • Lesser angle = greater elongation • Determine direction of travel • Pointed end (tail) points to the direction of travel.

  8. Blood Stain Patterns • Calculating Impact Angle • Determine L/W ratio • Use calculator or standard curve • A drop of blood hitting a surface at a 90◦ angle will give rise to a nearly circular drop, decreasing the angle, the stain becomes more elongated.

  9. Blood Stain Patterns Point of Origin The point of origin is essentially the location from which the blood that produced certain bloodstains originated. POO is a common point where multiple individual bloodstains can be traced. Lines are drawn through the long axis of the individual bloodstains, and the point where those lines converge is determined to be the point of origin.

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