Unintentional discharge

An accidental discharge (AD) occurs when there is a mechanical failure of the firearm. This can include things like firearms that do not have mechanisms to render them drop safe falling a sufficient distance,[1] a firing pin stuck forward,[2] a sear failing,[3] or rounds heating sufficiently to spontaneously ignite in the chamber (as may happen in a closed bolt machine gun).[4]

A negligent discharge (ND) is a discharge of a firearm involving culpable carelessness. In judicial and military technical terms, a negligent discharge is a chargeable offence. A number of armed forces automatically consider any accidental discharge to be negligent discharge, under the assumption that a trained soldier has control of his firearm at all times. This is the case in the United States Army,[5] Canadian Army, the Royal Air Force, the British Army and various Police Forces within the United Kingdom.

From an article on a U.S. Air Force website:

A negligent discharge occurs when a weapon is fired due to either operator error or a lack of attention to basic safety rules.[6]

• Safety area
• Queen's Regulations and Orders for the Canadian Forces

Forensic firearm examiners typically use more simplistic definitions limited to only 2 categories: unintentional discharge (no mechanical malfunction involved) and accidental discharge (mechanical malfunction involved).

• DiMaio, Vincent J.M. (2002). Gunshot Wounds: Practical Aspects of Firearms, Ballistics, and Forensic Techniques (2nd ed.). CRC Press. ISBN 978-1-4200-4837-7.
• Heard, Brian J. (17 August 2011). "4.7 Accidental Discharge". Handbook of Firearms and Ballistics: Examining and Interpreting Forensic Evidence. John Wiley & Sons. ISBN 978-1-119-96477-3.
• Hendrick, Hal W.; Paul Paradis; Richard J. Hornick (26 November 2007). "Chapter 2: Human Factors Causes of Unintentional Shootings". Human Factors Issues in Handgun Safety and Forensics. CRC Press. ISBN 978-1-4200-6297-7.
• Hueske, Edward E. (2016). "15: Officer-Involved Shootings". Practical Analysis and Reconstruction of Shooting Incidents. CRC Press. ISBN 978-1-4987-0766-4.
• Johnson, Brian R. (2007). Crucial Elements of Police Firearms Training. Looseleaf Law Publications. pp. 111–113. ISBN 978-1-932777-30-7.
• O’Neill, J., O’Neill, D. A., & Lewinski, W. J. (2016, November). A behavior analysis of unintentional discharges. The Police Chief, 83, 14-15. Retrieved from http://www.policechiefmagazine.org/research-in-brief-a-behavior-analysis-of-unintentional-discharges/
• O’Neill, J., O’Neill, D. A., & Lewinski, W. J. (2017). Toward a taxonomy of the unintentional discharge of firearms in law enforcement. Applied Ergonomics, 59(A), 283–292. doi: 10.1016/j.apergo.2016.08.013
• O'Neill, J., Hartman, M. E., O'Neill, D. A., & Lewinski, W. J. (2018). Further analysis of the unintentional discharge of firearms in law enforcement. Applied Ergonomics, 68, 267-272. doi: 10.1016/j.apergo.2017.12.004
• O’Neill, J., Hartman, M. E., O’Neill, D. A., & Lewinski, W. J. (2018, April). The ABCs of unintentional discharges. The Police Chief, 85, 14-15. Retrieved from http://www.policechiefmagazine.org/research-in-brief-the-abcs/
• O’Neill, J. (2018). Functional behavior assessment of the unintentional discharge of firearms in law enforcement. Journal of Organizational Behavior Management, 38(4), 275-287. doi:10.1080/01608061.2018.1514348
• Paulsen, J., (2017, March). 300 Negligent Discharges: Comprehensive Data Science. ConcealedCarry.com. Retrieved from https://www.concealedcarry.com/safety/300-negligent-discharges-comprehensive-data-science-reveals-gun-grabbers-and-gun-owners-are-both-wrong/