Chief Constable of Merseyside Police v McCarthy

Whether force used in self-defence or defence of another was reasonable requires a realistic evaluation of the whole rapidly developing incident. The court must recognise that reactions may be instinctive and must avoid minute retrospective dissection undertaken with the benefit of hindsight.

The doctrine of trespass ab initio is evidential. Later unlawful conduct makes an earlier lawful act unlawful only where it supports an inference that illegality was intended from the outset. Where force can be divided into an initially lawful application and a later excess, the lawful part does not become actionable merely because the later part was unlawful.

A police officer discharged a Taser at the respondent for approximately ten to eleven seconds during a violent disturbance. The Recorder found that firing the Taser and an initial five-second discharge were justified, but that continued discharge was excessive. He therefore held the Chief Constable liable in battery for the whole discharge.

The Chief Constable appealed from Manchester County Court and Family Court. The appeal concerned whether the Recorder could properly find the force unreasonable in light of the accepted threat confronting the officer and, alternatively, whether any unlawfulness extended retrospectively to the initially lawful five seconds. An unappealed finding of negligence concerning the respondent’s treatment after the discharge remained in place.

1. Appeal allowed unanimously. Hallett LJ held that the Recorder had set the standard of reasonable force too high. The officer was confronting a violent, noisy and rapidly developing incident. He fired the Taser because he reasonably believed that the respondent was about to attack others. He continued pressing the trigger after becoming distracted by an aggressive advance from another participant. On the Recorder’s factual findings, the prolonged discharge was reasonable in all the circumstances.

2. Assessment of reasonable force must reflect the realities confronting an officer required to act rapidly. A court must consider the rights of the person against whom force is used, the officer’s training and the urgency and danger of the situation. It should avoid close forensic dissection of a short period with the benefit of hindsight. The officer’s lack of an intention to prolong the discharge and his instinctive reaction to a new threat were material to the evaluative judgment.

3. Burnett LJ agreed and explained that civil self-defence requires the defendant to establish an honest and reasonable belief in the need to defend himself or another, together with force that was reasonable in all the circumstances. The Recorder had not drawn together his findings that the initial deployment was justified, that another man then menaced the officer, and that the officer consequently continued pressing the trigger without realising it. Those findings required the conclusion that the officer’s conduct was reasonable.

4. Burnett LJ further held that the doctrine of trespass ab initio is evidential rather than an absolute rule. Even if the final part of the discharge had been unlawful, that would not have converted the initial lawful five seconds into a battery. The Recorder had found that the officer intended no illegality at the outset, thereby negating the inference on which the doctrine depends. The President expressly endorsed this analysis. The battery claim therefore failed, while liability remained limited to the consequences of the officers’ unappealed negligence after the second discharge.

• Court of Appeal (Civil Division): The court allowed the Chief Constable’s appeal and set aside the finding of battery concerning the second Taser discharge. The unappealed finding of negligence after that discharge remained.
• Manchester County Court and Family Court: Recorder Allen QC found the initial use of the second Taser discharge justified but its continuation excessive. He held the Chief Constable liable in battery for the whole discharge.