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Gun Crime Investigation: "Firearms Examination" ~ 1970 FBI
🕑 Added 2019-09-11 00:17:06 +0000 UTCmore at http://quickfound.net/
Department of Justice. Federal Bureau of Investigation. 'TRAINING FILM: Shows techniques and methods used by FBI firearms investigation unit in identifying, comparing, and examining bullets, cartridges, firearms, residue, fingerprints, and other evidence for possible identification of weapons used in crimes.'
Originally a public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
https://en.wikipedia.org/wiki/Forensic_firearm_examination
Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/
Forensic firearm examination is the forensic process of examining the characteristics of firearms as well as any cartridges or bullets left behind at a crime scene. Specialists in this field are tasked with linking bullets and cartridges to weapons and weapons to individuals. Obliterated serial numbers can be raised and recorded in an attempt to find the registered owner of the weapon. Nitric Acid (HNO3) is the most common reagent used for this. Examiners can also look for fingerprints on the weapon and cartridges. Fingerprints are key pieces of evidence. If Crime Scene Investigators find prints at a scene, they will be dusted, photographed, collected, and analyzed both by hand (using comparison microscopes) as well as compared to databases for potential references.
By examining unique striations, scratches left behind on the bullet and weapon, individual fired rounds can be, but not always are, linked back to a specific weapon. These striations are due to the rifling inside the barrel of handguns. Rifling spins the bullet when it is shot out of the barrel to improve accuracy. Although striations are individualized evidence and will not match any other bullet or weapon, microscopic striations in the barrel of the weapon will change about every 3-5 shots. This is important because if attorneys wish to present ballistics evidence in court, it would be hard to prove beyond a reasonable doubt that one specific bullet would match one specific weapon. Forensic ballistics examiners may not fire more than 5 shots at most from a weapon found at a scene for this exact reason. Known exemplars taken from a seized weapon can be directly compared to samples recovered from the scene using a comparison microscope as well as newer 3-D imaging technology. Striation images can also be uploaded to any existing national databases. Furthermore, these markings can be compared to other images in an attempt to link one weapon to multiple crime scenes. Like all forensic specialties, forensic firearm examiners are subject to being called to testify in court as expert witnesses...
Fingerprint recovery from the surface of firearms is done with cyanoacrylate (more commonly known as superglue) fuming. Firearms are placed in a specially designed fume hood designed to evenly distribute fumes instead of removing them. Liquid superglue is placed in a container and heated until it is in a gaseous state. The circulating fumes adhere to the oils left behind by the fingerprint, turning the print white. The resulting white print can be enhanced with fingerprint powder to increase the contrast of the white print against the weapon's finish...
