The statutory test
Under s76 CJIA 2008, the question is whether the degree of force used was reasonable in the circumstances as the defendant believed them to be. Honest but mistaken belief still counts.
How the courts read it
Juries and courts look at proportionality, necessity, alternative options, and whether force was pre-emptive or reactive. Weapons and locations of strikes carry heavy weight.
Pre-emptive force
Waiting to be struck first is not required. If a reasonable person would believe an attack is imminent, force to prevent it can be lawful.
Physical intervention discipline
Only use techniques you are trained and certified in. Recognised systems (Maybo, Physical Skills Training) with current refresher training are the baseline.
Post-incident duties
Body-worn video, written statement, welfare check on the subject, RIDDOR consideration if injury, and notification to management within the shift.