Cartridges and Firearm Identification

Robert E. Walker

• Éditeur: CRC Press
• Année: 2012
• ISBN:
  9781466588813
• Édition: 1
• Sujet: Diritto
• Sous-sujet: Scienza forense

At a time when crime scene television shows are all the rage amongst the civilian population, knowledge of firearm forensics is of paramount importance to crime scene analysts, police detectives, and attorneys for both the prosecution and the defense. Cartridges and Firearm Identification brings together a unique, multidisciplined approach to quest

The World of Firearms and Ammunition

1

Introduction

Ammunition and firearms are broad, diverse, and dynamic topics. New products are regularly introduced to the marketplace; new companies appear on the landscape; and there is constant change. In addition, the uncommon, rarely seen older example comes out of the woodwork, occasionally challenging even the most knowledgeable person in the field so that, in effect, the students of these subjects must look in both directions to where the industry is at the moment and what has already transpired to round off their knowledge. Inevitably, the examiners who claim to have seen it all are taken to task when that which they did not know suddenly appears after they already thought they knew it all.

Ammunition and firearms are academic subjects unto themselves and can be viewed from any number of different viewpoints:

• Historians seeking to understand the implications and uses of firearms and how they affected past events
• Collectors of arms and ammunition seeking to expand their knowledge base about their particular interests and ascertain the value of the artifacts they hold
• Designers, engineers, and gunsmiths seeking to innovate and develop new products or improve an existing one
• Legislative and regulatory entities contemplating legislation or regulation with respect to firearms and ammunition
• Special-interest groups seeking to forward their respective agendas
• Law enforcement and investigative agencies focusing on the criminal aspects of the use of firearms and ammunition
• Marketers and users evaluating the suitability of firearms and ammunition for particular uses or markets: tactical, sporting, or otherwise

Balancing Firearm Safety with Evidence Preservation

The paramount consideration when handling firearms in any situation is safety. The devotion to safety overrides evidentiary and investigative concerns. Of course, the intent is always to avoid disturbing potential evidence, but a certain amount of handling is inevitable to ensure that an accident will not occur. In the case of firearms, the procedures needed to render them safe are, unfortunately, generally in the reverse order of those applied in preparation for safe use. Familiarity with the potential hazards can establish a comfort level that will allow the evidence collector to minimize the impact of safety considerations on the evidentiary value of the firearm.

In general, the rules for handling firearms are as follows:

1. Always treat a firearm as if it were loaded.
2. Always keep the muzzle of the firearm pointed in a safer direction.^*
3. Never press or allow anything to contact the trigger unless you are ready to and intent on discharging the firearm.
4. Never point a firearm at anything that you do not intend to destroy or damage.
5. Be sure of what your target is and what lies beyond.
6. Understand the mechanical and operational characteristics of the firearm you are handling.
7. Always ensure that the proper ammunition is used.
8. Ensure that the barrel is clear of obstructions before firing.
9. Never rely on the mechanical safeties of the firearm to prevent it from discharging.
10. Always handle the firearm in a diligent, conscientious manner.

For the law enforcement/investigative professional or firearm examiner, there are additional rules to consider given the context of evidentiary concerns, agency policies, and the particular circumstances under which the contact with the firearm has occurred. When encountering a firearm in an investigative context, the following procedures should be observed, keeping the basic rules of firearms safety in mind:

1. Document the condition of the firearm in situ^† by way of photographs and field notes.
   1. Does the firearm appear loaded or unloaded?
   2. Note the position of a manually selectable safety device, if the firearm is so equipped.
   3. Note the position of an external hammer, if the firearm is so equipped.
   4. Note the presence of a malfunction.
      Stovepipe: There is a spent casing stuck in the ejection port of a self-loading firearm. A stovepipe can have several root causes. From the perspective of a firearms instructor, the stovepipe indicates that the shooter is not maintaining a proper amount of grip pressure on the firearm to allow it to cycle, such as if the grip is relaxed while shooting or an insufficient amount of grip and wrist strength were applied during shooting, a condition often referred to as “limp wristing.” From the perspective of an investigator, the stovepipe condition may be observed in cases of suspected self-inflicted gunshot wounds because the person’s grip relaxed when the individual succumbed to the gunshot injury. It is important to note that the presence or absence of a stovepipe condition in such a scenario is not singularly indicative that the injury was self-inflicted, but rather it can be used in consideration of the totality of circumstances surrounding death or injury when an apparent suicide is being investigated.
      Double feed: A combination of live cartridge and spent casing in the chamber that jammed the firearm. As in the case of a stovepipe, the double feed has several root causes, and can be a shooter-induced error, a mechanical malfunction on the part of the firearm, a lack of preventive firearm maintenance, a magazine-related failure, or the result of ammunition with a powder charge below specification.
      Misfeed: A live cartridge did not properly load, causing the action to jam. Misfeeds are generally attributed to a firearm-related failure, such as a mechanical malfunction or maintenance issue; however, magazine-related issues cannot be ruled out, particularly a weak magazine spring. Misfeeds may also be the result of improperly sized ammunition being loaded.
      Misfire: A live cartridge failed to detonate in the chamber. A misfire can be caused by mechanical failure in the firearm, such as the firing pin or striker failing to contact the primer of the loaded cartridge, or the strike being weak and thus having insufficient pressure to cause detonation. A slight impression in the primer of the loaded cartridge will reveal a weak firing-pin strike. It may also be possible that the firing-pin surface is sufficiently worn to be incapable of operating as designed. Ammunition is the other possible cause, such as a bad primer, a primer that is harder than normal specification, a dud cartridge (no powder charge), or ammunition that has somehow been rendered completely inert, such as by exposure to the elements.
   5. If the firearm has a detachable ammunition magazine, is a magazine inserted?
   6. Note the presence of blood or other biological material that presents a biohazard to the handler.
2. When adequate documentation is made, pick up the firearm; keep away from the trigger and note additional observations as necessary.
   1. When handling handguns, it is often easiest to grasp the right and left sides of the grips.
   2. With long guns (rifles and shotguns), handling is often easiest by the edge of the stock and by the fore grip or hand guard forward of the trigger.
   3. If the action can be opened, do so slowly and carefully so as not to eject a chambered cartridge. If there is a cartridge in the chamber, take additional photographs with the action opened slightly to depict the presence of the loaded cartridge. When documentation is done, slowly close the action.
3. Identify and isolate the ammunition source. Determine where on the firearm the ammunition source is located. When the ammunition source has been identified, remove or unload the ammunition source.
   1. Remove the detachable magazine using the magazine release button or lever.
   2. Open the action of a breech-loaded firearm using the release lever, button, or knob.
   3. Open the cylinder of a revolver using cylinder-release mechanism, or remove the cylinder.
   4. Remove the magazine tube assembly from a tubular magazine and remove cartridges.
   5. Open the action of a belt-fed weapon and remove the belt.
   6. Slowly pull the slide back on a slide- or pump-action firearm. A loaded cartridge will reveal itself from the chamber. This should be done gradually, and the working of the action should be short, or not completely open. This process may require manipulation of an action bar release knob or lever to allow the action to open. If the firearm does not have separate loading and ejection ports, it may only be possible to slowly work the action to eject any loaded ammunition from the magazine.
   7. If the firearm is a bolt action, open or remove the floor plate from the internal magazine; caution should be exercised because the loaded cartridges will spill out. Otherwise, once the ammunition source has been identified and isolated from the action, open the bolt.
4. When the ammunition feed source has been isolated and removed, unload the chamber and leave the action open. Inspect the chamber visually and by feel, using a flashlight if necessary.
5. It may be required that the person clearing the firearm then band the weapon with a wire tie to visually confirm that the firearm is unloaded.

It is recommended, if possible, that two persons participate in rendering a firearm safe, even if one or both are fluent with firearms. One person handles the firearm while the second person can aid by having a camera handy to photograph the presence of the cartridge or casing in the chamber, which can be instrumental in certain types of investigations and recoveries. Figure 1.1 depicts an example of such an image; the action was slowly opened to reveal that a live cartridge was chambered, although no magazine was inserted in the weapon at the time it was inspected. In Figure 1.2, there is a ring of burnt powder surrounding the charge hole in the 12 o’clock position; however, the other charge holes do not indicate this same appearance, suggesting that only a single round had been discharged. Investigators should refrain from excessive handling or “dry” (unloaded) operations to the firearm (pressing the trigger, cycling the action, etc.) during the recovery phase. Consideration must also be given for the presence of latent fingerprints or potential DNA sampling, should the circumstances of the case call for it. The investigator is reminded that the recovery and documentation process should be treated as a “one time shot,” and evidence not collected at the time may not be available later if the need presents itself. It is inevitable that the evidence may be compromised to a certain extent due to the necessities of collecting and rendering the arm safe, and this must be factored into the equation as the cost of doing business. Investigators making the collection under more controlled circumstances can exercise more diligent handling. The first responding officers who must take control of a loose weapon in the interest of their own safety are not generally afforded this luxury.

Figure 1.1 (See color insert.) A semiautomatic rifle action is opened, revealing the presence of a live cartridge in the chamber. Such a find can be of great investigative interest. (Image from author’s collection.)

Figure 1.2 A close-up photograph of the front side of a revolver cylinder. Note the burnt powder ring around the charge hole at the twelve o’clock position. (Image from author’s collection.)

Crimes Involving Firearms and Ammunition

The value and accuracy of capturing and assessing accurate firearm and cartridge evidence early in the investigation cannot be understated. This statement must be balanced with other investigative, safety, and evidentiary concerns, as the condition of a firearm in situ is subject to change very quickly in the course of a criminal inquiry, so as many details as possible must be captured. In the criminal context, firearm-related crimes do not necessarily include the actual discharge of a firearm or that anyone was injured. Broadly, firearm-related crimes can be broken down into several categories, each with a subtly different evidentiary concern that supports the element of the crime:

1. Possession of a firearm or ammunition by a prohibited person:
   1. Unlicensed possession in venues were licensing or permits are required
   2. Possession by convicted felons whose civil rights have not been restored
   3. Persons adjudicated mentally incompetent
   4. Possession by a person who is an unlawful user of narcotics or who habitually uses narcotics
   5. Possession by illegal aliens
   6. Possession by underage persons
   7. Possession by a fugitive from justice
   8. Possession by a person who has renounced U.S. citizenship
   9. Possession by a person discharged from the armed forces under conditions other than honorable
   10. Possession by persons otherwise prohibited by statutory objection
   11. Possession in sterile areas such as airports, public buildings, and other similar places
2. Possession of an unlawful or contraband firearm:
   1. A firearm deemed unlawful by its present configuration
   2. Unregistered automatic weapons either as manufactured, converted, or remanufactured into such
   3. Unregistered firearm suppressors or silencers
   4. Unregistered improvised weapons
   5. A firearm with an obliterated, defaced, or altered serial number
3. Use of a firearm as an instrument in crime:
   1. Homicide
   2. Assault and battery
   3. Robbery
   4. Poaching
   5. Reckless or careless handling or display
   6. Storing of a firearm in a manner readily accessible by minors
   7. Situations involving culpable negligence
4. Ammunition of...