s20 Grievous Bodily Harm comes under the Offences Against the Person Act 1861 and is a triable either way offence.
s20 GBH: "Whoever shall unlawfully and maliciously wound or inflict any grievous bodily harm upon any person shall be guilty of an offence and shall be liable to imprisonment for not more than 5 years"
s20 GBH is by unlawfully wounding or unlawful infliction of grievous bodily harm.
The mens rea for s20 GBH is that the harm must be "maliciously" caused.
Wounding is a "break in the continuity of the skin".
JCC v Eisenhower
The wounding must be "serious harm".
Saunders.
Psychiatric harm can be GBH provided that the harm is "serious".
Burstow.
Infliction was defined by Lord Hope as having the same meaning as cause.
There is biological GBH which can be the transmission of STIs.
Removing the requirement for common assault led to the development of biological GBH.
Dica.
"Maliciously" means intentional or reckless.
Cunningham.
The defendant only needs to foresee that "some" harm might occur.