Case Facts
The claimant brought an action in trespass for assault, battery, and maihem against the defendant. The defendant pleaded son assault demesne — that is, that he struck in his own defence. It was admitted by the court that son assault demesne was a good plea in maihem; the sole question before the King's Bench was what quality or degree of initial assault would be sufficient to maintain such a plea in the context of maihem.
Held
The court held that the plea of son assault demesne requires proportionality between the initial assault and the defendant's retaliatory response. Where two parties close immediately following a blow and in the ensuing scuffle one party maihems the other, the plea of son assault demesne may be sustained. However, where only a minor blow is struck by the claimant and the defendant responds by inflicting a maiming injury upon the claimant, that disproportionate response will not satisfy the plea. A small or trivial initial blow cannot justify a retaliatory act that amounts to maihem.
Ratio Decidendi
The ratio of the case is the principle of proportionality in self-defence. The plea of son assault demesne is available in an action for trespass including maihem only where the initial assault was of such a nature and gravity as to endanger the defendant's life or to justify the degree of force used in response. Where the assault was merely a little blow, a retaliatory act of maiming cannot be excused under the plea of son assault demesne. As the court articulated: if A strikes B and B immediately strikes back, and they close at once so that in the scuffle B maihems A, that constitutes son assault demesne. But if A delivers only a minor blow to B and B responds by inflicting a maiming injury upon A, the plea will not avail B, for the response is wholly disproportionate to the provocation received. The underlying rationale, affirmed by Powell J, is that son assault demesne is a good plea in maihem precisely because the initial assault must have been of such a character as to have endangered the defendant's life — without that quality of threat, the severe retaliatory force cannot be justified.
This principle constitutes an early and authoritative statement in English law that the right of self-defence is not unlimited: the force employed in response to an assault must be proportionate to the threat faced. A defendant who retaliates with excessive force, disproportionate to the attack made upon him, cannot rely upon self-defence as a complete answer to an action in trespass.
The principle established in this case has been considered and applied in subsequent tort law decisions concerning self-defence and the use of force in response to an assault, including Green v Goddard (1702), Lane v Holloway [1968], and Co-Operative v Pritchard [2011].
Obiter Dicta
Not applicable.