What does the lawfulness of using fatal force in self-defense depend on according to AG v. Keatley (1954)?

In AG v. Keatley (1954), the lawfulness of using fatal force in self-defense hinges primarily on the necessity of that force. The court established that a defender is justified in using such force only if it is deemed necessary to prevent an imminent and unlawful attack. The assessment surrounding necessity evaluates whether the response was proportionate to the threat faced and whether there were alternative means available for the defender to avoid using lethal force.

In this specific context, the necessity criterion implies that if the defender's life is genuinely under threat and no other options are available to neutralize that threat, the use of fatal force may be legally justified. Thus, the overarching principle from this case emphasizes that the crucial factor is not necessarily the provocation or whether the individual was armed, but rather whether the response was necessary in the circumstances.

The focus on necessity ensures that self-defense claims are carefully scrutinized to ensure that individuals do not resort to excessive force when lesser measures may suffice, thus maintaining a balance between the right to self-defense and the imperative to minimize violence.