Explainer: What Mental State is Required to Commit a War Crime?

What exactly is the definition of war crimes under international law or, more precisely, what mental state is required to commit such an offence? The synopsis below provides an answer with respect to military strikes that result in civilian casualties and destruction of civilian property.

Many posts at Just Security refer and often depend analytically on the definition of war crimes. I hope this synopsis will serve as a handy reference point. I will be linking back to this discussion in future posts, including one later today on US and UK support for Saudi-led operations in Yemen.

Let’s start with a couple axioms: Not all military strikes involving civilian casualties, even if expected and significant in number, are violations of the law of armed conflict. Not all violations of the law of armed conflict are war crimes.

It is useful to consider potential law of armed conflict violations along a kind of spectrum:

I. War Crimes: Willful killing

Willful killing includes purposefully targeting civilians. It also includes situations in which an attacker employs a targeting procedure that he or she knows cannot effectively distinguish between civilians/civilian objects and legitimate military targets. Categories 2 and 3 below include recklessness, for example, when the attacker consciously disregards a substantial and unjustifiable risk of the harm to civilians and civilian objects.

1. Engaging in an attack with the purpose of killing civilians or destroying civilian objects

2. Engaging in an attack with the knowledge that the probable consequence will be to kill civilians or destroy civilian objects in violation of the principle of distinction*

3. Engaging in an attack with the knowledge that the probable consequence will be to kill civilians or destroy civilian objects in violation of the principle of proportionality**

II. Other violations of the law of armed conflict not amounting to a war crime

4. Engaging in an attack in which the attacker should have known the probable consequence would be to kill civilians or destroy civilian objects in violation of the principle of distinction

5. Engaging in an attack in which the attacker should have known the probable consequence would be to kill civilians or destroy civilian objects in violation of the principle of proportionality

6. Failure to take all feasible precautions to minimize harm to civilians and civilian objects

Note: Categories 4 and 5 include ordinary negligence or lack of foresight.

* The principle of distinction: Parties to a conflict must at all times distinguish between civilians and combatants. Attacks may be directed only against combatants and military objects. Attacks must not be directed against civilians or civilian objects.

** The principle of proportionality: Parties to a conflict must refrain from attacks in which the expected loss of life or injury to civilians, and damage to civilian objects incidental to the attack, would be excessive in relation to the concrete and direct military advantage expected to be gained. 

About the Author(s)

Ryan Goodman

Co-Editor-in-Chief of Just Security, Anne and Joel Ehrenkranz Professor of Law at New York University School of Law, former Special Counsel to the General Counsel of the Department of Defense (2015-2016). You can follow him on Twitter @rgoodlaw.