This is a common law offence which means that it does not come under particular legislation. The law surrounding it is from case law rather than legislation by parliament.

If you look at what must be proved that is basically what the law is in relation to this charge.

There is then a lot of case law that explains this law in greater detail.

(b) The fighting or violence was such that a bystander of reasonable firmness and courage might reasonably be expected to be terrified.

(a) Duress.

(b) Factual dispute.

(c) Honest and reasonable mistake of belief.

(d) Identification dispute.

(e) Lack of intent.

(f) Mental impairment.

(g) Necessity.

(h) Self-defence.