Firearms Evidence Chapter 8 PDF

FIREARMS EVIDENCE Chapter 8 SAFETY RULE There is no such thing as an “unloaded” firearm! Treat all firearms as though they are loaded! What is Firearms Evidence? Firearms Cartridge components Fired and unfired Gunshot residue on targets Discharge residues on the hands of...

FIREARMS EVIDENCE Chapter 8 SAFETY RULE There is no such thing as an “unloaded” firearm! Treat all firearms as though they are loaded! What is Firearms Evidence? Firearms Cartridge components Fired and unfired Gunshot residue on targets Discharge residues on the hands of individuals who have fired or handled a discharged firearm Firearms Evidence Usually encountered in crimes against persons Homicide, assault, and robbery Othertypes of crimes include burglary, rape, and narcotics violations Themost common firearms involved in criminal cases are handguns Revolvers and semiautomatic pistols Some involve long arms Shotgun or rifle  Revolver: Smith and Wesson.38 cal. 5 shot Semi-Automatic: Ruger.380 Auto with loaded magazine (Photos courtesy of: Michael G. Bessette, MS – Criminal Justice Contributor) Long Arm Rifles Firearm Cartridges Consist of the: Cartridge case Primer Propellant (gunpowder) Bullet or projectile Eachcomponent may become physical evidence in a shooting case Bulleted Cartridges Areproduced in many configurations and sizes for both centerfire and rimfire weapons Cartridges Rimfire (RF) cartridges have the priming compound encased around the rim Centerfire(CF) cartridges have the priming compound encased as a central primer and may have a rimmed, rimless, or semi-rimmed cartridge case Headstamp identifies manufacturer & cartridge type Three General Cartridge Shapes Straight, Tapered, Bottlenecked All.22 rimfire cartridges and most centerfire cartridges have straight cases Most centerfire rifle cartridges have a bottlenecked shape, the tapered case is largely obsolete Cartridge Cases and Bullets Propellant Grains aka Gunpowder Manufactured with various shapes for rimfire and centerfire ammunition Theshape of the propellant grain influences the burning rate of the propellant Propella nt Shapes for Small Arms Shotshells Plastic shell filled with: Shot (projectiles) Wad Gunpowder Primer Pair Share Question In this course, cases are often mistakenly referred to as shells. What are the implications if this were to happen at a crime scene? Characteristics of Rifled Barrels Named because of the “rifling” produced in the bore of the barrel Rifling consists of lands and grooves Grooves are scraped out or compressed down Lands are the raised areas They twist to make the bullet spin to stabilize it Characteristics of Rifled Barrels Shotguns have no rifling in their barrels and are considered a smooth bore weapon Class Characteristics of Firearms Caliber Number of lands and grooves Width of the lands and grooves Direction of twist Also rate of twist Family Characteristics of Firearms Firearmsthat share the same class characteristics establish the family characteristics of a certain make and model of firearm Example: family of firearms that have 6 L/G, right twist, and specific width of L/G belong to the same family of firearms that have the same caliber and these same characteristics Firearm Caliber Expressedas bore diameter (d) or groove diameter (D) Measuredin either hundreds or thousands of an inch2 Sometimes the barrel diameter may be different from the caliber.38 Special has a bore of.36 inches Class Characteristics of Fired Bullets Consist of caliber, # L/G, direction of twist Directresult of the barrel’s rifling being impressed into the bullet’s circumference as it is forced down the barrel during discharge The impressions on the bullet are referred to as land impressions and groove impressions Class Characteristics of Fired Bullets Field Estimation of Bullet Caliber If not distorted, can compare to a calibrator estimator Only compare if there is NO trace evidence! Fired Cartridge Cases Have an impression of the breech face An ejector mark from the ejector Override and gouge marks from the extractor Cartridgecases fired in semiautomatic, automatic, and revolvers will typically have: Chamber striations produced by the forced removal from the chamber Firing pin impression Marks on Expended Cartridge Cases Participation Question When labeling cartridge case evidence at a crime scene, how important to you think it is to document the information on the headstamp? Lab Examinations of Firearm Evidence Identification of the firearm that fired or the cartridge Muzzle to target distance determinations Gunshot residue identifications Weapon functionality examinations Bullet trajectory and/or sequence of firing determinations Collection of Firearms Evidence Safety is the most important consideration Always treat any firearm as though it is loaded This means: Never point it at anyone (point it down) If you’re not comfortable, ask for help If you’re not familiar with the firearm, ask for help If the firearm is stuck or jammed, ask for help Safe or Unsafe? Note-taking and Evidence Marking Document the location and condition of the firearm Loaded or unloaded? Hammer cocked? Safety on or off? Makea sketch of the area showing location of all items of evidence Photographs should be taken of the firearm prior to disturbing its location except in extreme emergency Note-taking and Evidence Marking Unload the firearm safely, noting: Ammunition in the chamber? Loaded magazine in semi-auto? Cartridge cases or ammunition in revolver? The weapon should be identified by recording the make, model, serial number on a tag tied to the trigger guard Collection of Firearms Evidence After examining for fingerprints, bloodstains, or other trace evidence, take extreme care to unload the weapon Touch areas not likely to retain fingerprints Handle knurls or checkered grip Slide Unloading Revolvers Markcylinder to indicate which was in line with the barrel Recordthe position of each round in the cylinder in your notes Package each separately Indicate chamber location on evidence packaging Diagram of Recovered Revolver Unloading Autoloading Firearms Point the gun down Release the magazine Pull back slide to release the ammunition in the chamber Package separately: Firearm Magazine Don’t remove ammunition! Ammunition from chamber Collection of Firearms Evidence Weapons found in water Placed in a container with the same water covering the weapon If the weapon is removed from the water and allowed partially to dry the rusting process may begin rapidly Transporting to the Lab Personal delivery is preferred A loaded handgun may be transported in a specially constructed box that is able to hold the firearm securely in place If the firearm is to be sent by mail, it must be unloaded, securely packaged, and clearly marked Live ammunition cannot be shipped vis US Mail Recovery of Fired Ammunition Components Bullets embedded in wood or plaster Sketch the location of the bullet hole Cut/saw out the wall portion with the bullet DO NOT dig it out! Removal from deceased persons (ME) X-ray body Remove with rubber-tipped or plastic forceps, or fingers Bullet is packaged as is Examined for trace at the lab Recovery of Fired Ammunition Components Cartridge case location Important for reconstruction Sketch and measure the position of all ejected cartridge cases Package each separately Shot wads (shotguns) Travelbehind the shot Same method for ejected T 1 T T 9 0 T T 6 cartridge cases 5 7 T 4 T T 3 8 T 1 T 2 Recovery of Fired Ammunition Components Shot pellets Ifembedded, process as embedded bullets Dig out only if necessary Rubber tipped or plastic tweezers Live shot shells or cartridges Submit all found ammunition that is related to the case Boxes of ammunition The labs needs identical ammunition for testing Pair Share Question You find boxes of live ammunition at a crime scene, and you ask your partner to collect them. While traveling back to the lab, your partner indicates that he did not collect the boxes because he didn’t think it was important. All you have are photos of the boxes. Is this still helpful to the lab? Gunshot Residues (GSR) Result from the discharge of a firearm Include components from the primer, powder, projectile material, and products of their combustion Components exit through any opening Gunshot Residue Production Gunshot Residues (GSR) The amount of residue varies with the type of firearm, ammunition, and conditions of discharge Cheaply made revolvers will produce the most amount of GSR The use of shotgun or rifle may produce gunshot residue on the shooter’s cheek Gunshot Residue Analysis Methods Neutron Activation Analysis (NAA) Bombard with neutrons, analyze the radiation given off Atomic Absorption analysis (AA) Analyzes chemical extracts for barium and antimony Scanning electron microscopy/energy dispersive x-ray analysis (SEM/EDX) Scans disc for particles & analyzes them Collection of Gunshot Residues Can be found on a living person several hours after firing Consider all GSR lost after 6 hours Process the subject’s hands as soon as feasible The subject should not be allowed to wash or rub their hands prior to sampling GSR can be removed easily Collection of Gunshot Residues Ifhands cannot be processed right away, place new, clean, brown paper bags over the subject’s hands and tape the bag to the wrist Never use plastic bags on a live subject since the production of sweat will destroy any residues present Plastic bags may be used on deceased subjects It is important that the investigator remember to wash their hands and put on gloves prior to sampling for gunshot residues Procedure for GSR Collection Using Metal Disc Do this before swabbing for AA analysis Wash your hands & wrists, wear the gloves provided in the kit 1. Remove the protective cover 2. Press the sticky portion lightly onto the hand repeatedly until the disc is no longer sticky 3. Seal the disc in the provided container 4. Repeat for other areas GSR Collection with Discs for SEM Analysis Procedure for GSR Collection Using Swabs Put on gloves before touching anything from the kit 1. Add nitric acid to the acid control swabs, place back into the container 2. Remove one swab from the “right back” tube. Moisten with 5% nitric acid solution. 3. Swab the back of the right hand in one direction, rotating the swab in between swipes 4. Swab the rest of the hand back using the other swab. Place swabs into the container. Procedure for GSR Collection Using Swabs 5. Repeat for the other hand 6. Repeat for the palms of the hands 7. Do not touch the blank swab GSR Collection With Swabs for AA Analysis Trace Metal Detection Test For those who are suspected of holding, but not shooting Searches for trace metals present on the firearm Spray suspected hand with trace metal reagent, expose to shortwave UV light When a color develops, photograph the pattern Distance Determinations When the distance between a gun muzzle and target is an issue Suicide, struggles Varyingamounts of GSR from the barrel goes onto the surface depending on this distance Note and sketch location, photograph pattern with ruler Target Discharge Residues Package all garments separately Collection of Target Residue on: Clothing – Paper wrap and seal with tape Bedding – Paper wrap and seal with tape Solid objects – Photograph, sketch, and collect Make cardboard “tent” to protect the pattern Skin – Photograph and collect with a GSR kit Participation Question Provide one example of an instance where a distance determination can prove or disprove a story. Example: The victim/suspect/witness said ________ happened. The distance determination showed that ________ happened.