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Firearms

Firearms. http://youtu.be/jjUTZH_Vdxs. Firearms Identification. A discipline mainly concerned with determining whether a bullet or cartridge was fired by a particular weapon. Thompson Submachine gun. Bullet Comparisons.

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Firearms

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  1. Firearms http://youtu.be/jjUTZH_Vdxs

  2. Firearms Identification A discipline mainly concerned with determining whether a bullet or cartridge was fired by a particular weapon.

  3. Thompson Submachine gun

  4. Bullet Comparisons Every bullet can be matched to a particular weapon through comparing striation marks http://youtu.be/VZxLApQ2Rb4

  5. Cartridge & Components

  6. Striations are made through a process called rifling. (Major development in firearms) Spiral grooves are either cut or impressed upon the bore of a barrel to create the distinct lands and grooves. (This was added to increase stability in the projectile which increased accuracy) With each impression, microscopic markings are made within the bore to make each gun have a unique set of striation marks.

  7. With the aide of the comparison microscope, an expert can make several points of comparison: Striation marks between the recovered bullet and the test bullet of questioned gun Number of lands and grooves and their direction of twist Same caliber

  8. Firearms

  9. Shows primer strike pattern where firing pin hit primer

  10. The caliber is the diameter of the gun barrel. Caliber is normally recorded in millimeters. These are 9mm Lugar casings

  11. Unlike rifled firearms, shotguns have a smooth barrel. They usually fire small lead balls or pellets contained within a shotgun shell, but can also shoot solid projectiles know as slugs. The gauge of a shotgun is the diameter of the barrel.

  12. Firing Process Primer explodes Powder ignites Gases build up Bullet is pushed from cartridge case to back of barrel Bullet is forced down the barrel by the expanding gases Cartridge case is slammed against breech face Imperfections in barrel and on breech face are transferred to surfaces of bullet and cartridge case

  13. Functioning of a Firearm Video compliments of www.firearmsid.com and Hi-Point firearms

  14. How they test fire guns for comparison into a tank of water.

  15. Automated Firearm Search Systems DRUGFIRE— developed for the FBI to examinethe unique markings of spent cartridge casings Integrated Ballistics Identification System (IBIS)—developed for the ATF, digital images of identifying features found on both spent bullets and cartridge casings National Integrated Ballistics Information Network (NIBIN)—new unified system incorporating both IBIS and DRUGFIRE

  16. Info on IBIS and Weapons tool marks http://youtu.be/yAlixegkf0o

  17. Distance Determination Visual - The process of determining the distance between the firearm and the target, usually based on the distribution of powder patterns or the spread of a shot pattern. Chemical - Modified Greiss – looks for nitrates, nitrites - Sodium Rhodizinate – looks for lead

  18. DISTANCE – 9ft .

  19. DISTANCE – 15 ft

  20. DISTANCE – 30 ft

  21. distance ~ 8 ft- SHOTGUN

  22. Gunpowder Residues When a firearm is discharged, unburned and partially burned particles of gunpowder in addition to smoke are propelled out of the barrel along with the bullet towards the target.

  23. Methods Used To Detect GSR On Hands Dermal Nitrate (Paraffin) Test - Developed 1933, quickly disproved - False positives with cigarette ash, urine, face powder, prepared foods - Continues to be used in some jurisdictions Atomic Absorption Spectrophotometry(AAS) - Looks for presence of barium (Ba), antimony (Sb), and lead (Pb) - Is not specific for GSR

  24. Methods Used To Detect GSR On Hands Scanning Electron Microscopy (SEM) - Identifies particles which are presently considered unique to GSR - Involves both visual and chemical idntification Organic Methods - Being used with “leadless” ammunition; looks for nonmetal components of GSR - Most techniques are still in development http://youtu.be/ObroUJsTzEE

  25. Serial Number Restoration Serial numbers are impressed into firearms for identification. To restore a serial number that has been removed or obliterated, the area must be thoroughly cleaned and polished. An etching reagent is applied which will react with the strained area faster than the unaltered metal, allowing the numbers to appear.

  26. Collection and Preservation of Firearm Evidence Firearms Safety is the most important precaution, preventing all accidental discharge of a loaded weapon in transit. All firearm evidence should be marked for identification with evidence tag attached to the trigger guard. Firearm recovered from an underwater location should be transported submerged in the water found to prevent rust.

  27. Ammunition Bullets recovered at a crime scene are scribed with the investigator’s initials and should be wrapped in tissue paper before transport to protect any trace evidence. The exact location of shell casings should be noted.

  28. Gunpowder Deposits A firearm victim’s clothing must be preserved to prevent damage or disruption to the gunpowder residues deposited around the bullet hole. Wet clothing should be air dried out of direct sunlight and then folded for protection. Each item should be placed in a separate paper bag.

  29. EXTRA THINGS TO REMEMBER WHEN COLLECTING FIREARMS EVIDENCE • Never stick anything in the barrel • Assume all firearms are loaded • Unload before fingerprinting • Don’t overlook possibility of fingerprinting cartridges and cases • Don’t forget the possibility of DNA • Package items separately

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