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Firearms Examiner Training. Dillon JH, Jr. 2013. Firearms Examiner…

- - - - Based on striations and/or impressions produced during the normal functioning of a firearm, it is possible to identify
        
        a. Cartridge cases and shotshell cases as having been fired in a particular firearm, based on firing pin impressions, breech face marks, and chamber marks.
        
        b. Fired and unfired cartridge cases and shotshell cases as having been cycled through the action of a particular firearm, based on extractor and ejector marks as well as other mechanism marks.
    - - Since 1925, significant advances and developments include
        
        a. Optical systems and peripheral equipment for comparison microscopy.
        
        b. Digital imaging and management.
        
        c. More formal and structured definitions of the criteria for identification.
        
        d. Advances in computer hardware platforms and database software to link serial shootings.
        
        e. Digitized ammunition reference resources available on the Internet and on storage media.
    - - Cycle of fire
        
        a. Feeding of a cartridge manually or from a magazine
        
        b. Chambering of a cartridge
        
        c. Locking of the breech or bolt mechanism
        
        d. Firing by releasing of the firing pin
        
        e. Obturation, specifically, sealing of powder gases forward of the cartridge case or shotshell case by expansion of the cartridge case to fully fill the chamber, as well as by expansion of projectiles or wadding material
        
        f. Unlocking of the breech or bolt mechanism
        
        g. Extraction of the fired cartridge/shotshell case
        
        h. Ejection of the fired cartridge/shotshell case
        
        i. Cocking of the firing mechanism
      - Striated marks occur when there is relative motion between two objects under pressure.
      - Impressed toolmarks (compression marks) occur when a tool is placed against another object and sufficient force is applied to the tool that an impression is made.
    - - Firing pin impressions
        
        a. Indentation of the primer of a centerfire cartridge case or the rim of a rimfire cartridge case when struck by the firing pin
      - Firing pin drag marks
        
        a. Striated toolmarks produced when a projecting firing pin contacts a cartridge or shotshell during extraction or ejection
      - Breech face marks
        
        a. Negative impression of the breech face of the firearm found on the head of the cartridge case and/or primer after firing.
      - Primer shearing marks
        
        a. Striated toolmarks caused by the rough margins of a firing pin hole (aperture) scraping the primer metal during unlocking of the breech of a firearm
      - Chamber marks
        
        a. Individual microscopic marks placed on a cartridge case by the chamber wall as a result of chambering, expansion during firing or extraction
      - Extractor marks
        
        a. Striated toolmarks produced on a cartridge or cartridge case from the operation of an extractor (usually found on or just ahead of the rim)
      - Ejector marks
        
        a. Toolmarks produced on the head of a cartridge case, from contact with the ejector (generally at or near the rim).
      - Anvil marks
        
        a. Microscopic marks impressed on the forward face of the rim of a rimfire cartridge case as it is forced or compressed against the breech end of the chamber by the firing pin.
      - Ejection port marks
        
        a. Striated marks produced by hard contact between the ejection port of a firearm and a rapidly moving ejected cartridge case.
      - Magazine marks
        
        a. Striated marks produced on the periphery of a cartridge as it moves from the lips of a magazine towards the chamber during feeding.
    - - Individual Characteristics
        
        a. Examination and identification are based on these principles
        
        i. The various parts of the operating mechanism of firearms (firing pin, breech face, chamber, extractor, ejector, and other areas) can bear unique microscopic characteristics as a result of manufacturing processes, use, and abuse.
        
        ii. These characteristics may mark the surfaces of fired and unfired cartridge cases/shotshell cases with striated marks or impressions as they are fired in or cycled through the firearm.
        
        iii. These individual characteristics may be reproducible and may be uniquely identifiable with a particular firearm.
        
        b. Marks produced by the random imperfections or irregularities of tool surfaces. These random imperfections or irregularities are produced incidental to manufacture and/or caused by use, corrosion, or damage. They are unique to a particular tool and distinguish it from all other tools. Tool refers to the various parts of the action and mechanism of a firearm.
        
        i. Accidental characteristics is a term formerly used to mean individual characteristics
      - Class Characteristics
        
        a. Measurable features of a specimen that indicate a restricted group source. They result from design factors and are therefore determined prior to manufacture. Location, size, orientation, and relationship of the various parts of a firearm are some class characteristics of interest.
      - Subclass Characteristics
        
        a. Discernable surface features of an object that are more restrictive than class characteristics because they are
        
        i. Produced incidental to manufacture
        
        ii. Significant because they relate to a smaller group source, that is, a subset of the class to which they belong
        
        iii. Identifiable within a time frame since manufacturing processes change over time
        
        b. If faced with the possibility of subclass influence, the examiner should
        
        i. Research the manufacturing processes related to a particular make and model
        
        ii. Consult with peers regarding the firearm in question
        
        iii. Research pertinent literature, especially the AFTE Journal
    - - Needs
        
        a. Establish an identification as to a common source
        
        b. Conveying results to a jury
        
        c. Justifying results to a jury
    - - 1.Criteria
        
        a. The expectations of more sophisticated jurors
        
        b. The need for more objective identification criteria
        
        c. The changing environment of the courtroom following Daubert v. Merrell Dow Pharmaceuticals
        
        d. The potential for increased credibility for examiners in the courtroom
    - - Three principles
        
        a. Pertains to toolmarks enables opinions of common origin to be made when the unique surface contours of two toolmarks are in sufficient agreement
        
        b. The sufficient agreement is related to the significant duplication of random toolmarks as evidenced by the correspondence of a pattern or combination of patterns of surface contours.
        
        i. Product of the examiners personal training, skills, and experience in
        
        • Recognizing corresponding patterns of matching striations
        
        • Recognizing corresponding patterns within impressed toolmarks
        
        • Determining the best known non-match in their personal experience
        
        • Training and experience in comparing striated and impressed toolmarks
        
        c. The current interpretation of individualization/identification is subjective in nature, founded on scientific principles and based on the examiners training and experience.
      - AFTE Range of Conclusions
        
        a. Two broad categories
        
        i. An evidence cartridge case or shotshell case from a crime scene is identified as having been fired in a particular evidence firearm
        
        ii. Evidence cartridge cases or shotshell cases recovered from the same or separate incidents are identified as having been fired in a single firearm (no firearm submitted).
        
        • Fired Case Examination
        
        b. Accepted for all types of toolmark comparisons
        
        i. Identification
        
        • "Agreement of a combination of individual characteristics and all discernable class characteristics where the extent of agreement exceeds that which can occur in the comparison of toolmarks made by different tools and is consistent with the agreement demonstrated by toolmarks known to have been produced by the same tool."
        
        ii. Inconclusive
        
        • Some agreement of individual characteristics and all discernable class characteristics, but insufficient for identification
        
        • Agreement of all discernable class characteristics without agreement or disagreement of individual characteristics due to an absence, insufficiency, or lack of reproducibility
        
        • Agreement of all discernable class characteristics and disagreement of individual characteristics, but insufficient for an elimination
        
        iii. Elimination
        
        • "A significant disagreement of discernable class characteristics and/or individual characteristics. For purposes of fired cartridge case and shotshell case comparisons, an elimination is most often based on observed differences in any class characteristic."
        
        iv. Unsuitable for comparison
        
        • This outcome is appropriate for fired and mutilated cartridge cases and shotshell cases that do not bear microscopic marks of value for comparison purposes.
    - - Procedure
        
        a. Review laboratory protocols, as needed
        
        b. Complete administrative requirements
        
        i. Chain of custody
        
        ii. Marking of evidence
        
        iii. Laboratory case identifiers
        
        iv. Investigative file identifier
        
        v. Examiner identity
        
        vi. Quality assurance
        
        c. Follow laboratory safety protocols
        
        d. Determine the presence of trace evidence and follow laboratory protocol for collection
        
        i. Examples
        
        • Paint
        
        • Glass
        
        • Blood
        
        • Bone
        
        • Soft tissue
        
        • Hair
        
        • Fibers
        
        • Wood
        
        • Metal smears
        
        • Masonry
        
        • Stone
        
        e. Determine if latent fingerprint examinations should be performed prior to toolmark examinations
        
        f. Determine if other examinations (not requested) should be performed. If so, coordinate with the investigator
      - Comparison
        
        a. Ensure that stereo and comparison microscopes meet all maintenance and calibration standards
        
        b. Select an appropriate level of magnification for both objective lenses of the comparison microscope. Typically, this setting will be 1x or 2x. Ensure that the objective lenses are locked in place.
        
        c. Select the appropriate for both ocular lenses. This would be typically be 10x.
        
        d. Select the same type and orientation of light source for each comparison microscope stage. Many examiners prefer strong fluorescent or fiber-optic lighting.
  - - - Chain of custody
      - Laboratory safety
      - Trace evidence
        
        a. Coordination of examination sequencing across disciplines to preclude loss of trace evidence
      - Evidence marking and packaging
    - - Basic descriptive information.
    - - Stereo and comparison microscopes should be calibrated and maintained prior to examination.
      - Range facilities
      - A variety of ammunition
      - Appropriate containers for fired test standards
      - Metal or electric scribes and permanent markers
      - Stereomicroscope with a range up to approximately 30x
      - Microscope lighting options
      - Video monitor and live video/closed circuit television capability for the comparison microscope
      - Imaging equipment to record and document areas of correspondence
    - - Performed according to laboratory protocol.
    - - Suitable for comparison, but not always sufficient for identification.
    - - They are obtained and appropriately marked and preserved.
      - Most forensic firearms laboratories maintain a collection of known standards, referred to as the standard ammunition file, or SAF.
  - - - Mount one of the test cartridge cases or shotshell cases on the right stage with the base oriented upwards.
      - Orient the light source to illuminate the marked area of the base obliquely.
      - At low magnification (10x-20x), carefully examine the base and primer area. Rotate the cartridge case or shotshell case slowly around its long axis to find the best areas of individual characteristics on the primer and/or the surrounding base area. Once the best area is located, the case should remain in that position on the right stage.
      - Mount another test cartridge case or shotshell case on the left stage and rotate it on its long axis until it is in the same orientation as the case on the right stage.
      - Adjust the light source for the left stage at the same oblique lighting angle as the light source for the right stage.
      - Manipulate both microscope stages so as to align any corresponding microscopic impressions or striated marks that may be present on the primers and/or the base areas. If corresponding microscopic detail is present for comparison purposes, the examiner can then conclude whether or not there is sufficient agreement in the quality and quantity of the individual characteristics to substantiate an identification. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
      - To further evaluate the potential value of test cartridge cases and shotshell cases, the firing pin impressions should also be examined and compared. In order to better illuminate the interior of firing pin impressions and to compensate for depth-of-field limitations of the microscope, it may be necessary to tilt both test specimens relative to their respective light sources. It will be necessary to incrementally rotate both cartridge cases around their long axes in order to fully evaluate the microscopic detail within the firing pin impressions. In some cases, it can be productive to cast firing pin impression surfaces in order to detail subtle marks that are not readily visible except by casting. Mikrosil is one example of casting material especially valuable for this purpose.
      - If corresponding microscopic detail is present for comparison purposes on the firing pin impressions, the examiner can then conclude whether or not there is sufficient agreement in the quality and quantity of the individual characteristics to substantiate an identification. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
      - In addition, the extractor marks, ejector marks, chamber marks, magazine lip marks, anvil marks, ejection port marks, and other possible mechanism marks should be evaluated. A comparison of these marks may require a number of reorientations on the microscope stages in order to best view the areas of interest.
      - As with the other comparisons, if corresponding microscopic detail is present, the examiner can then conclude whether or not there is sufficient agreement in quality and quantity of the individual characteristics for identification of the test cartridge cases or shotshell cases as having both been fired in the same firearm or cycled through the action of the same firearm, depending on the type of mark being identified. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
    - - Observed the types of microscopic marks being produced by an evidence firearm
      - Assessed the quality of these marks for comparison purposes
      - Noted the peculiarities of the particular firearm
      - Documented the pertinent observations
  - - - Determine that the evidence cartridge case or shotshell case does have microscopic marks of value for comparison purposes and is suitable for comparison.
      - Determine if the test cartridge cases or shotshell cases can or cannot be identified with each other.
      - Mount the best test cartridge case or shotshell case on the right stage with the base oriented upwards.
      - Orient the light source to illuminate the marked area of the base obliquely.
      - At low magnification (10x-20x), carefully examine the base and primer area. Rotate the cartridge case or shotshell case slowly around its long axis to find the best areas of individual characteristics on the primer and/or the surrounding base area. Once the best area is located, the case should remain in that position on the right stage.
      - Adjust the light source for the left stage at the same oblique lighting angle as the light source for the right stage.
      - Mount an evidence cartridge case or shotshell case on the left stage and rotate it on its long axis until it is in the same orientation as the test cartridge case or shotshell case on the right stage.
      - Confirm that the evidence and test cartridge cases or shotshell cases bear consistent class characteristics as far as location, size, and type of marks. If the class characteristics are the same, the examination should proceed.
      - Manipulate both microscope stages to align any corresponding microscopic impressions or striated marks that may be present on the primers and/or the base areas. If corresponding microscopic detail is present for comparison purposes, the examiner can then conclude whether or not there is sufficient agreement in the quality and quantity of the individual characteristics to substantiate an identification. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
      - The area of the best agreement should be documented according to laboratory protocol.
      - If the evidence cartridge case or shotshell case is damaged or deformed in some way, it may be necessary to use other areas of evidence and test items for comparison purposes.
      - To further evaluate the potential value of test cartridge cases and shotshell cases, their firing pin impressions should also be examined and compared. In order to better illuminate the interior of firing pin impressions and to compensate for depth-of-field limitations of the microscope, it may be necessary to tilt both test specimens relative to their respective light sources. It will be necessary to incrementally rotate both cartridge cases around their long axes in order to fully evaluate the microscopic detail within the firing pin impressions.
      - If corresponding microscopic detail is present for comparison purposes on the firing pin impressions, the examiner can then conclude whether or not there is sufficient agreement in the quality and quantity of the individual characteristics to substantiate an identification. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
      - In addition, the extractor marks, ejector marks, chamber marks, magazine lip marks, anvil marks, ejection port marks, and other possible mechanism marks should be evaluated. A comparison of these marks may require a number of reorientations on the microscope stages in order to best view the areas of interest.
      - As with the other comparisons, if corresponding microscopic detail is present, the examiner can then conclude whether or not there is sufficient agreement in quality and quantity of the individual characteristics for identification of the test cartridge cases or shotshell cases as having both been fired in the same firearm or cycled through the action of the same firearm, depending on the type of mark being identified. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
    - - The evidence cartridge case or shotshell case was fired in different firearm.
      - Damage occurred to the evidence cartridge case or shotshell case that caused distortion, deformation, or elimination of microscopic detail.
      - The test ammunition used was significantly different from the evidence, causing a difference in the way the test cartridge case or shotshell case was marked.
      - The evidence firearm was damaged between firing of the evidence and test cartridge case or shotshell case.
    - - Changing the brand and type of ammunition being used to obtain test specimens.
      - Cleaning the evidence firearm and re-firing test cartridge cases or shotshell cases.
  - - - Determine that the evidence cartridge case or shotshell case does in fact have microscopic marks of value for comparison purposes and is suitable for comparison.
      - Mount the best evidence cartridge case or shotshell case on the right stage with the base oriented upwards.
      - Orient the light source to illuminate the marked area of the base obliquely.
      - At low magnification (10x-20x), carefully examine the base and primer area. Rotate the cartridge case or shotshell case slowly around its long axis while seeking the best areas of individual characteristics on the primer and/or the surrounding base area. (Higher magnifications can be used later to verify the correspondence of finer impressed or striated detail.) When the best area is found, let the cartridge case or shotshell case on the right stage remain in that position.
      - Adjust the light source for the left stage at the same oblique lighting angle as the light source for the right stage.
      - Mount another evidence cartridge case or shotshell case on the left stage and rotate it on its long axis until it is in the same orientation as the evidence cartridge case or shotshell case on the right stage.
      - Confirm that the evidence cartridge cases or shotshell cases bear consistent class characteristics with regard to location, size, and type of marks. If the class characteristics are the same, the examination should proceed.
      - Manipulate both microscope stages so as to align any corresponding microscopic impressions (e.g., breech face marks) or striated marks (e.g., primer shearing) that may be present on the primers and/or the base areas of the evidence cartridge cases or shotshell cases. If corresponding microscopic detail is present for comparison purposes, the examiner can then conclude if there is sufficient agreement in the quality and quantity of the individual characteristics to substantiate an identification. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
      - The area of the best agreement should be documented, preferably by digital or conventional photography, or by sketching or narrative according to laboratory protocol. Images should be marked with the examiner's initials, case identifier, degree of magnification, evidence, and test item numbers, and a description of what is portrayed.
      - If the evidence cartridge cases or shotshell cases are damaged or deformed in some way, it may be necessary to use other areas of evidence and test items for comparison purposes.
      - To further compare the evidence cartridge cases or shotshell cases, their firing pin impressions should also be examined and compared. In order to better illuminate the interior of firing pin impressions and to compensate for depth-of-field limitations of the microscope, it may be necessary to tilt the evidence specimens relative to their respective light sources. In addition, it will be necessary to also incrementally rotate both cartridge cases around their long axes in order to fully appreciate the microscopic detail within the firing pin impressions. In some cases, it can be productive to cast firing pin impression surfaces in order to detail subtle marks that are not readily visible except by casting. Mikrosil is one example of casting material especially valuable for this purpose.
      - Again, if corresponding microscopic detail is present for comparison purposes, the examiner can then conclude whether or not there is sufficient agreement in the quality and quantity of the individual characteristics to substantiate identification. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
      - In addition, the extractor marks, ejector marks, chamber marks, magazine lip marks, anvil marks, ejection port marks, and other possible mechanism marks should be compared. A comparison of these marks may require a number of reorientations on the microscope stages in order to best view the areas of interest on the evidence items.
      - Yet again, if corresponding microscopic detail is present for comparison purposes, the examiner can then conclude whether or not there is sufficient agreement in the quality and quantity of the individual characteristics to substantiate an identification. The corresponding areas should be indexed using a permanent felt tip marker for possible future reference.
  - - - Inappropriate interchangeability
        
        a. In some cases, cartridge interchangeability is safe and possible by design; in other cases, this is unsafe and inappropriate.
    - - Reloading toolmarks
        
        a. Cartridge case holding tools: These tools physically grip cartridge cases by the base while in a reloading press.
        
        b. Resizing tools: These tools are used to compress fired cases which were slightly expanded during obturation back to their precise original dimensions.
        
        c. Crimping tools: These tools are used to slightly crimp the mouth of cartridge cases to bullets in some loads.
      - Manufacture/assembly factors
        
        a. Manufacturing marks on primers: Repetitive marks may be noted on the surface of fired primers. These are actually due to the processes for manufacturing primers and have nothing to do with the discharge of a firearm. These marks will almost never remain in the same relationship to the class characteristics left on the fired cartridge. Manufacturing marks can also be distinguished by the fact that they often extend into a firing pin impression.
        
        b. Bunter marks: These are marks made by the die which produces the headstamp on rimfire cartridge cases or the headstamp and primer pocket on centerfire cartridge cases. These marks have nothing to do with marks produced by a firearm, but they do allow an examiner to state that two headstamps were produced by the same die.
    - - Use of adapters
        
        a. Adapters in the form of a sleeve may be inserted into the barrel of a firearm permitting the use of alternative cartridge types. In this scenario, chamber marks would be the focus of examination if the sleeve were recovered.
      - Substitution of parts
        
        a. Replacement of pistol components: If pistol parts such as the firing pin, extractor, ejector, chamber, or slide were replaced, cartridge cases fired in the pistol in its original condition would no longer be identifiable with the firearm.
        
        b. Revolver cylinders: In an even simpler operation than replacement of pistol parts, the replacement of a revolver cylinder would change a whole set of chamber marks.
      - Modifications
        
        a. Refiling of parts: If firearm parts such as the firing pin, extractor, chamber, or slide were to be refiled or otherwise abraded, cartridge cases fired in the firearm in its original condition would no longer be identifiable with the altered part.
      - Manufacturer-related factors
        
        a. Subclass characteristics: If the influence of subclass characteristics cannot be eliminated as a possibility, identifications of cartridge cases or shotshell cases may not be possible.
        
        b. Ultrasmooth machining techniques: In many cases involving highly polished surfaces, there may be no marks of value present for comparison purposes. This is frequently noted in new firing pins and in some brands of firearms.
    - - Microscopic marks
        
        a. Loaded into and extracted from a particular firearm
        
        b. Loaded into and removed from a magazine integral to or associated with a given firearm
      - Reasons
        
        a. A decision to remove a cartridge from the chamber as part of the normal unloading process
        
        b. An effort to clear a misfire
        
        c. An effort to clear a misfeed
        
        d. A criminal unconsciously leaving courage marks by repeatedly cycling ammunition through the action prior to the commission of a crime
        
        e. Other reasons best known to a criminal prior to the seizure of a firearm by law enforcement.
      - Worksheets
        
        a. Similar to fired cartridge cases and shotshell cases except
        
        i. Any references to chamber marks or breech face marks would be accompanied by a not applicable entry on the worksheet
        
        ii. Any reference to firing pin impressions would most often be accompanied by a none observed entry
  - - - Unsolved case file
      - Open case file
      - Reference fired specimen file
      - Open case ammunition file
    - - IBIS