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Firearms/Toolmarks

 

The Firearms and Toolmarks Section is responsible for the comparison of firearms, casings, projectiles and other evidence that may be associated through toolmarks. Toolmarks result whenever two items come into contact with sufficient force, such that one or both of the items bear markings resulting from the other item.

The most important method utilized in the Firearms and Toolmarks Section is comparison microscopy, which allows two items to be viewed simultaneously. Evidence projectiles, casings, and other items bearing toolmarks are compared to known items in order to determine consistency or inconsistency, both in class characteristics and individual characteristics.

CAPABILITIES AND SERVICES

Mechanical Condition of Firearm

Each firearm that is submitted to the firearm section is examined to determine whether it is in mechanical operating condition and it is test fired, when possible. This examination includes the operability of the safety features, physical characteristics of the firearm and trigger pull. In addition, examinations can be conducted to determine whether the firearm will or will not fire without pulling the trigger, when necessary. Also, capability of full automatic fire is determined.

Identification of Firearm Parts

Firearm parts found at a crime scene may be identified as to:
a. The type of firearm from which they originate

Identification of Brand

Bullets, wad components, cartridge cases and shotshells recovered at a scene or from a body may be identified by brand.

Possible Brand and Caliber of Firearm

By determining the class characteristics (caliber, number of lands and grooves, direction of twist and their dimensions, breechface and/or firing pin shapes, other various markings) exhibited on fired ammunition components (bullets, cartridge cases, shotshells), the firearm examiner may be able to provide information concerning the brand and type of firearm which the component was fired. This may be particularly useful
when no firearm has been recovered.

Bullet Identification to a Particular Firearm

When a rifled firearm is manufactured and through its use, unique toolmarks are left on the inner surface of the barrel. When the firearm is fired, striated marks are engraved in the bullet. These striae are individual to a particular firearm.
 
When a firearm is submitted to the laboratory for comparison, the examiner test fires the firearm and uses a comparison microscope to compare the striae of the test fired bullet to those present on the evidence bullet. By this microscopic study of the markings on both bullets, the examiner can determine if the evidence bullet was fired from the submitted firearm. The following conclusions may be reached:
  1. The bullet was identified as having been fired from the firearm.
  2. The bullet was eliminated as having been fired from the firearm.
  3. It is not possible to identify or eliminate the bullet as having been fired from the firearm.

Firearm not Recovered

Bullets and cartridge cases/shotshells recovered from the same or different incidents can be compared to determine if they were fired from/in the same firearm.

Bullet Fragments

The firearm examiner may be able to provide the same type of information from a bullet fragment as that of a whole bullet. A bullet fragment can be identified as having been fired from a particular firearm if sufficient marks are present. The quantity and quality of these marks are determined by microscopic examination. All bullet fragments should be collected and submitted to the laboratory.
 

Cartridges

If the cartridge has been cycled (loaded, extracted and ejected) through the action of a bolt- action, lever- action, slide-action or autoloading firearm, the markings left by this process may be associated with a particular firearm. In some cases markings left on cartridges may be associated to a particular magazine. If these types of marks are present on cartridges, it may also be possible to associate them to cartridge cases, if no firearm has been recovered.

Cartridge Cases

Generally, there are five surfaces of a firearm that may leave identifiable marks on various areas of a cartridge case: breechface, firing pin, extractor, ejector, chamber. Generally, if a fired cartridge case can only be identified to a particular firearm by the extractor and/or ejector mark(s), this only identifies the cartridge case as having been extracted and/or ejected (i.e., cycled) in a particular firearm.

Identification of Possible Brand of Firearm

By determining the class characteristics (caliber, type of breechface marks and firing pin shape) exhibited on a fired cartridge case, the firearm examiner may be able to provide information concerning the type and brand of firearm which fired the cartridge case(s). This may be particularly useful when no firearm has been recovered.

Shotshells

These may be associated to a firearm in the same manner as cartridges. The gauge may be
determined and the brand of the components may be characterized.

Discharged Shotshells

These may be identified in the same manner as a fired cartridge case. In addition, the components that may have been commercially loaded into the shotshell may be identified.

Shotshell Components

Recovered wad material and/or projectiles may be identified as to gauge, type, and/or brand of commercial manufacture.

Distance (Proximity) Determination

The approximate distance the muzzle of a firearm was from an object at the time of firing may be determined by examining clothing or other materials for the presence of gunshot residues. Gunshot residues are discharged from the firearm in the form of burnt, partially burnt and un-burnt gunpowder particles, vaporous lead, and particulate metals. When packaging objects thought to contain gunshot residues, use packaging techniques that protect the surface and minimize cross-contamination.
 
Generally, the firearm and all ammunition components associated with the firearm should be submitted along with the object to allow for a thorough examination for approximate distance. If no firearm is available for submission, the laboratory can still examine the object for the presence of gunshot residue. However, distance determination when no firearm is available is limited to contact gunshots.
 
Pellet patterns can also be examined for distance determination based on the rate of pellet spread over a given distance for a particular weapon and ammunition.
 

Reconstruction/Trajectory Analysis

The analysis of objects brought to the laboratory can be conducted to aid in the investigation for determination of trajectory and origin of the shots fired, help locate other pertinent evidence, and helpdetermine the position of the victim and/or the shooter.
 
Firearms/Toolmark procedure manuals are located in a tab under the Quality Assurance section of the webpage. They can be accessed by clicking here.
FIREARMS Collection Guidelines

ITEM - Firearms (handgun or shoulder gun)
METHOD - All firearms to be submitted to the laboratory should be made safe.  Unload firearms after properly documenting the cylinder in revolvers or the chamber and magazine in pistols, rifles and shotguns.  Package firearms in a rigid container, seal, mark container and indicate condition of firearm on container as LOADED or UNLOADED.  Firearms submitted for DNA must be sealed with tape over all edges and any openings (such as holes in the box) prior to submission (see example in General Submission of Evidence).
DISCUSSION - Safety is the first consideration; therefore, firearms should be unloaded prior to delivery to the laboratory. If this is not possible, call the firearm supervisor to discuss.  Packaging material may rub latent prints and destroy evidence; therefore, it is important to package in a manner so the gun contacts the packaging material as little as possible.  Documenting the cylinder in a revolver may help determine the sequence of events and aid in scene reconstruction. It is requested that you not package guns in plastic.

ITEM – Bullets, shot pellets, slugs and shotshell wads
METHOD - Recover using rubber tipped forceps or latex examining gloves, so as not to contaminate or add trace or other biological evidence.  Place in a plastic ziplock type bag.  Package projectiles separately, clearly label and seal properly.  It is currently suggested not to mark the item itself.  Bullets, etc. collected from doctors in the emergency room should be washed off with water (not disinfectants) prior to submission and air dried before packaging.  Body fluids may destroy some microscopic markings.
DISCUSSION - Handling these items with your fingers may add additional trace or biological evidence.  Bullets, etc. should be handled as if biohazards are present and in a manner to protect any DNA that may be present.  The chain of custody can be maintained by marking the packaging material and carefully noting your actions.

ITEM - Cartridge, cartridge case, shotshell
METHOD - Recover using rubber tip forceps or gloves so as not to obliterate fingerprints, or damage trace evidence.  Cartridges, cartridge cases, and shotshells may be placed in a ziplock bag if fingerprints are not a concern.  Properly label and seal the container.  If fingerprints are a concern, package in a manner that will immobilize the item and/or reduce the contact with the packaging material.  Never mark the headstamp area or other portions of the cartridge, cartridge case, or shotshell.  In incidents where the use of saboted ammunition is suspected, the investigator should be aware that the sabot may have separated from the projectile (bullet or slug).
DISCUSSION - Handling these evidence items may destroy fingerprint evidence.  The marks in the headstamp area and other portions are used in the laboratory comparison and identification process.  Ammunition found at the scene or in the suspect’s house may be helpful in the comparison process.  The sabot bears the identifying marks (the bullet/slug in this instance does not).

ITEM - Clothing for gunpowder/gunshot residues related to distance (proximity) determination
METHOD - Completely air dry the clothing.  Place clothing item flatly onto a clean piece of butcher paper sufficiently larger than the item itself.  Properly label and seal the container.  Also, please submit the autopsy report from the M. E., the police report, room size, constraints, witness/suspect statements, and any information that may be pertinent to the investigation.
DISCUSSION - This packaging approach ensures that the area of the clothing bearing the gunshot residue will not come in contact with other areas of the garment.  This is also a good procedure for bloody garments.  Plastic will cause the biological material on the clothing to deteriorate, even if it is thoroughly air dried.

 
TOOLMARKS Collection Guidelines

ITEM - Toolmarks
METHOD - If the object bearing the toolmark is reasonably mobile, bring the entire object to the laboratory.  Protect the toolmark area by covering it carefully with paper; however, always consider latent fingerprints when packaging.  If the object is particularly large or is completely immobile, the toolmark area may be cut out (depending on the situation, e.g., security considerations and damage to property) or cast using a suitable casting material.  Package the toolmark cast in a rigid container (such as a pill box), properly seal and label. Include mid-range or orientation photographs, sketches and reports.
DO NOT place suspect tool into toolmark as it could destroy markings.
DISCUSSION - The actual toolmark is preferred over a cast of the toolmark; therefore, the microscopic marks need to be protected to provide the best possible results.  Placing the tool into the toolmark may destroy microscopic detail. Submission of photographs, sketches and reports may help the examiner determine the action of the tool.

ITEM - Tools
METHOD - Package in a manner to protect the working end of the tool (e.g., on a screwdriver place a paper fold over the tip).  After the working end has been protected, place in a rigid container.

FRACTURE MATCH Collection Guidelines

ITEM - Items to be examined for fracture match (examples: broken tools, glass, vehicle parts, etc.)
METHOD - Package in a manner that will protect the edges of the items to be fracture matched.  For example, when submitting glass, wrap and package each piece separately and clearly label and seal.  In the request clearly indicate which items should be compared.  For fragile items, such as paint, a rigid container cushioned with tissue is probably best.
DISCUSSION - The edge will contain the areas to be fracture matched.  If these areas are damaged it may prevent any possibility of a successful match.

OBLITERATED SERIAL NUMBERS Collection Guidelines

ITEM - Obliterated Serial Numbers
METHOD - Protect the area needing restoration.  Do not attempt to restore the number in the field.
DISCUSSION - The first attempt to restore the number is the most productive and further attempts will likely destroy the evidence.
 

What is Forensic Firearm Identification?

Forensic Firearm Identification is a discipline of forensic science which has as its primary concern to determine if a bullet, cartridge case, or other ammunition component was fired by a particular firearm.

What is Forensic Toolmark Identification?

Forensic Toolmark Identification is a discipline of forensic science which has as its primary concern to determine if a toolmark was produced by a particular tool.

Why are Firearm Identification and Toolmark Identification usually performed within the same group of examiners?

The process of matching bullets and cartridge cases to the gun that fired them is the same process used in matching toolmarked items with tools. In both disciplines the examiner looks for impressed and striated toolmarks on items of evidence. From an identification standpoint a firearm is merely a specialized tool which imparts striated toolmarks on bullets and impressed toolmarks on cartridge cases.

What kind of training and education is required to work as a Firearm and Toolmark Examiner?

Minimal educational requirements include a four year college degree in a natural science or chemistry along with the specialized post-college training in Forensic Firearm and Toolmark Examination. The typical post-college training program is a two-year instructor-student arrangement provided by one of the larger crime laboratory systems. The Firearms Examiner Academy offered by the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) is an accelerated program which couples an experienced bench examiner with a new hire who attends an intensive study program at the BATFE laboratory in Maryland.

Can a bullet or cartridge case be positively matched to a gun to the exclusion of all other guns of the same type?

Yes, that is the core of the work performed by an examiner. However, it is not always possible to match a bullet or cartridge case to the gun that actually fired it. Such factors as impact damage, barrel fouling, and corrosion can make it difficult or impossible to make the positive association.

How is it possible to match a bullet or cartridge case to a particular gun seeing that a gun manufacturer may produce thousands of identical firearms?

Manufacturing processes produce gun barrels and gun breechfaces which conform to a mechanical standard, however, on a microscopic level the surfaces in a gun barrel or on a gun breech possess randomness as a result of such factors as the crystalline structure of the metal, machining defects, and the like. This randomness is the source of unique impressed and striated toolmarks created by each different firearm.

In addition to matching bullets and cartridge cases to guns what other types of evidence are processed by an examiner?

Muzzle-to-target distance determinations, serial number restorations, shooting incident reconstructions, physical matchings.

Is it possible to determine the type of firearm used in a crime by examining bullets and cartridge cases alone?

Yes, discharged cartridge cases and fired bullets display "class characteristics". Examining a bullet will reveal such data as the caliber, the number of lands and grooves from the rifling, the approximate land to groove ratio, the direction of rifling twist. Cartridge cases display the caliber designation and may also display characteristics unique to a particular firearm class.

What items are necessary for a muzzle-to-target distance determination?

On clothing it is necessary to assure that any moisture/body fluids on the garment are air-dried as quickly as possible to prevent deterioration of any gunshot residue products. Minimizing significant variables is necessary to assure the most reliable results. This is accomplished by providing the firearm and ammunition used in the commission of the shooting event.

On human skin it is necessary to provide high quality, properly exposed photographs of the residue pattern from a variety of angles. In addition to numerous overall photos from a variety of angles, a set of photos with a scale from the "trajectory perspective" - photos taken along the path followed by the bullet - is required.

Should crime guns be unloaded prior to submitting them to the laboratory?

As a general rule, yes. However, in some cases unloading a gun may jeopardize DNA, trace, or other evidence. In those cases it is necessary for the gun to be hand-carried to the lab where it can be tended to upon receipt. Loaded guns can never be mailed or otherwise shipped by common carrier. Loaded guns cannot be put into storage at the lab without prior special approval.

Can a gun that has been submerged in a lake, river, or the ocean be successfully matched to fired ammunition components?

Yes, the lab was successful in matching bullets and cartridge cases to a pistol that was submerged for exactly one year in a Mat-Su valley lake. Special handling of the firearm insured success. Submerged guns must remain completely submerged during the recovery process to prevent oxidation. Once the gun is removed from the water at the laboratory it is immediately flushed of debris, cleaned, completely dried, and re-oiled. Damp firearms tend to rust rapidly, quickly negating the possibility of a positive association of the gun to bullets and cartridge cases.

Can a fired bullet be matched back to the specific cartridge case that it was originally loaded in?

In theory, one should be able to find toolmarks from the case mouth on the fired bullet. In practice, toolmarks left on the bullet by the cartridge case are effectively eliminated by the rifling in the gun barrel.

Can live cartridges be compared to discharged cartridge cases or fired bullets?

Yes, it is important for the lab to have access to ammunition like that used in a shooting incident. A positive identification may hinge on the use of the exact same ammunition. Often the only source of this ammunition is the suspect. When ammunition is available, it should be seized along with the suspect firearm.

Can you determine when a firearm was last fired?

No, there is no practical test available to put an exact date on a discharge. However, revolvers often display "fresh flares" on the face of the cylinder. This finding often establishes the number of shots fired during the last use of the gun. As cylinder flares age they dull and are frequently rubbed or otherwise degraded during handling.

Can you determine the caliber of a bullet by the hole it produces?

Sometimes. Certain materials will preserve the exact diameter and cross sectional profile of the bullet. Aluminum street sign material often reveals the caliber and rifling class of the firearm that fired the perforating bullet. Other materials, such as clothing, plastic, rubber, etc. are too elastic. Large bullets can produce deceptively small holes. Each case is considered individually.

Can a Firearm Examiner prove murder?

No. Murder is the intentional taking of a human life. Laboratory testing cannot determine the intent of the individual holding the firearm when it discharged. It is the responsibility of a trial jury to consider the testimony of all of the witnesses, including the Firearm Examiner, and to consider the arguments put forward by the prosecutor and defense attorney in order to reach a verdict of murder, manslaughter, criminally negligent homicide or acquittal.

Does the lab or its examiners work civil cases or criminal cases outside of Alaska?

No. The lab is limited to processing evidence collected in the course of criminal investigations submitted by local, state, and federal law enforcement agencies located within Alaska. The current firearm/toolmark staff do not moonlight in their specialty.

Where can I find additional information about Forensic Firearm and Toolmark Identification?

You can contact the lab staff by phone or email. Additional resources can be found by visiting http:\\www.afte.org and http:\\www.firearmsid.com.

What is NIBIN?

Read about ATF's NIBIN proagram

Visit the National Integrated Ballistic Information Network website