Author: John H. Dillon, Jr.

Jack Dillon earned a B. S. from the United States Naval Academy and an M. Ed. from the University of Virginia. Commissioned in the United States Marine Corps in 1964, he attained the rank of Captain of Marines. Appointed a Special Agent, FBI, in 1970, he investigated diverse criminal violations, including organized crime, bank robberies, extortions, and kidnappings. In 1976 he received orders to the Firearms/Toolmarks Unit of the FBI Laboratory for training as an examiner, where he evaluated evidence and provided on-site field support in domestic cases, as well as abroad. He also designed and taught basic- and management- level forensic courses at the FBI Academy, Quantico, Virginia, 1982-1988. Jack retired from the FBI as Chief of the Firearms/Toolmarks Unit in 1994, and continues to work as a consultant in forensic firearm cases and in training design and delivery.

Introduction

This module addresses forensic firearm examinations relating primarily to the following categories of firearm-related evidence:

• Cartridge-related evidence:
  • Fired cartridge cases (the portion of a fired cartridge left behind after a bullet has been fired, often referred to as brass in a nonforensic context)
  • Unfired cartridges (unfired ammunition that is still complete, consisting of a projectile, propellant, primer, and a cartridge case assembled as a unit, often referred to as a round in a nonforensic context)
• Shotshell-related evidence:
  • Fired shotshells (shotshell cases that no longer contain propellant, pellets, buckshot, wadding, buffer, or a shotgun slug)
  • Unfired shotshells (intact shotshells that consist of the shotshell case, primer, powder, pellets, buckshot, wadding, buffer, or a shotgun slug assembled as a unit)

Objectives

At the conclusion of this module the student will be able to do the following:

• Describe the potential evidentiary value of reproducible striations and/or impressions produced during the normal functioning of a firearm
• Define the procedure for the microscopic comparison of the class and individual characteristics of firearms reflected on fired and unfired cartridge cases/shotshell cases
• List the equipment and facilities necessary to microscopically compare fired and unfired cartridge cases/shotshell cases
• Describe the marks that may be present on cartridges and shotshells as a result of being
  • cycled through the action of a firearm,
  • fired in a firearm.
• Articulate how the following concepts relate to the formulation of examination conclusions of fired and unfired cartridge cases and shotshell cases:
  • Class characteristics
  • Individual characteristics
  • Subclass characteristics
  • Pattern identification
  • AFTE Theory of Identification
  • Sufficient agreement
  • Best known nonmatch
  • Consecutive matching striae (CMS)
  • Impressed marks
  • AFTE Range of Conclusions
• Explain the differences between the following terms in regard to comparisons of fired and unfired cartridge cases and shotshell cases:
  • Identification
  • Inconclusive
  • Elimination
  • Unsuitable
• Define the contents of a typical fired cartridge case/unfired cartridge comparison worksheet for documentation of examination notes
• Describe the content and formats for reporting of results of comparisons of microscopic marks on fired and unfired cartridge cases/shotshell cases in terms of the AFTE Range of Conclusions
• Discuss in general terms the Integrated Ballistics Identification System (IBIS) in regard to preliminary remote comparisons (computer correlations) of cartridge cases/shotshell cases and case linkage in serial shooting cases

AFTE Knowledge and Ability Factors

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