A more thorough explanation:

Definition: "Wilful killing" is a war crime that is defined in the Rome Statute for the International Criminal Court. To prove a case of wilful killing, the following elements must be present:

• A killing of one or more persons
• The victims were protected under the Geneva Conventions of 1949
• The perpetrator knew that the victims were protected under the Geneva Conventions
• The conduct was associated with an international armed conflict

For example, if a soldier intentionally kills a prisoner of war who is protected under the Geneva Conventions during an international armed conflict, this would be considered wilful killing and a war crime.

Another example would be if a military commander orders his troops to attack a civilian population that is protected under the Geneva Conventions during an international armed conflict, resulting in the deaths of innocent civilians. This would also be considered wilful killing and a war crime.

These examples illustrate the definition of wilful killing by showing that the victims were protected under the Geneva Conventions, the perpetrator knew of this protection, and the conduct was associated with an international armed conflict.