This article contains instructions, advice, or how-to content. (December 2014)
An unintentional discharge is the event of a firearm discharging (firing) at a time not intended by the user. An unintended discharge may be produced by an incompatibility between firearm design and usage, such as the phenomenon of cooking off a round in a closed bolt machine gun, a mechanical malfunction as in the case of slamfire in an automatic weapon, or be user induced due to training issues or negligence. The phenomenon has also been defined in scientific literature as an activation of the trigger mechanism that results in an unplanned discharge that is outside of the firearm’s prescribed use. Where prescribed use refers to departmental policies and laws related to the operation of firearms (O'Neill, 2018).
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, a firing pin stuck forward, a sear failing, or rounds heating sufficiently to spontaneously ignite in the chamber (as may happen in a closed bolt machine gun).
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, 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.
Forensic firearm examiners typically use more simplistic definitions limited to only two 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.
- 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.
- 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.
- Drop test a sig p320 yes it goes BANG!! 1st time on carpet!. dennis1979gm. 8 August 2017. Archived from the original on 19 November 2020. Retrieved 2 October 2021 – via YouTube.
- SKS Firing Pin Sticks Forward. Murraysguns. 18 February 2015. Archived from the original on 27 December 2020. Retrieved 2 October 2021 – via YouTube.
- How to accidentally discharge your pistol properly. GPS. 18 December 2016. Archived from the original on 2 July 2021. Retrieved 2 October 2021 – via YouTube.
- Ammunition Cook-Off. SmallArmsUser. 18 July 2017. Retrieved 2 October 2021 – via YouTube.
- Trevino, Abel. "Proper Weapons Practices Key to Ending Negligent Discharge Incidents in Iraq." army.mil. United States Army. 1 March 2007. 
- Cunningham, Vernon (9 January 2014). "Negligent discharge: Don't be that guy". Joint Base Elmendorf-Richardson, USAF. Retrieved 18 December 2014.