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Crime Scene Photography by Professor Bob Warnock and Jerry Dambrogio. Gun Shot Residue Class.

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Crime Scene Photography by Professor Bob Warnock and Jerry Dambrogio

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Presentation Transcript


Crime Scene Photography

by

Professor Bob Warnock

and Jerry Dambrogio


Gun Shot Residue Class

  • Gunshot residue (GSR), or more technically, gunshot primer residue, is expelled as tiny particles from the barrel of a firearm when it is fired. Among other materials, gunshot residue contains the heavy metals barium, lead and antimony. Modern forensic methods require the presence of these metals to identify trace evidence as gunshot residue.

  • Through the 1990s the presence of two or more of these heavy elements was sufficient to conclude the chemicals were the result of a gunshot. New, more rigorous standards for gunshot residue testing are now being required by many courts. The trend is toward a standard that requires the presence of at least one Pb-Ba-Sb particle (lead-barium-antimony) exhibiting characteristic GSR morphology and supported by a sufficient number of atomically identified GSR supporting particles in the remaining particle population.

  • Investigators may test a suspect's hands, arms and face for particles of gunshot residue as evidence of having recently handled or fired a gun. Current testing methods are inconclusive as a suspect's clothing or body can easily become contaminated after the firing from sources such as being handled by police officers or being transported in contaminated police vehicles


Facts of the case

Suspect

Scene Weapon

Victim


Probative Forensic Analysis

Suspect

Scene Weapon

Victim


Gunshot Residue

- Materials which are emitted from a firearm when it is discharged.


Gunshot Residue

- Materials which are emitted from a firearm when it is discharged.


Forensic Uses

  • Distance determination

    • “Was the victim shot at close range?”


Forensic Uses

  • Distance determination

    • “Was the victim shot at close range?”

  • Identification of bullet holes

    • “Is the damage due to the passage of a bullet?”


Light Microscopy

  • Microscopic examination

    • Smokeless powder

    • Fiber damage


Forensic Uses

  • Association with a firearm discharge

    • “Who fired the gun?”


Gunshot Residue

  • There has been a critical need for a reliable and accurate way to associate a suspect with a firearm discharge


Smokeless Powder

  • 1933 Teodoro Gonzalez

    • Criminal Identification Laboratory- Mexico City Police Headquarters

      • Gonzalez test

      • Paraffin test

      • Paraffin glove test

      • Diphenylamine test

      • Dermal nitrate test


Smokeless Powder

  • Nitrates


Scanning Electron Microscopy


Scanning Electron MicroscopySignals Generated in the Scanning Electron Microscope

SAMPLE


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