Sections 20 and 18 of the Offences Against the Person Act 1861 deal with the offences of “wounding” or inflicting “grievous bodily harm with intent”.
Section 20 makes it an offence for someone to unlawfully and maliciously wound or inflict grievous bodily harm upon any other person, with or without any weapon or instrument.
In this context unlawfully means without excuse or justification at law. Maliciously means ill will or with evil motive; it requires either an actual intention to do the particular kind of harm that was done or recklessness whether any such harm should occur or not.
An accused is reckless in this context if he is aware that his actions risk inflicting grievous harm on a person but (s)he nonetheless goes on to take the risk.
A wound means any break in the continuity of the whole skin although small cuts are normally charged as “actual bodily harm”.
Grievous bodily harm
Grievous bodily harm means serious or really serious harm. Bodily harm can include psychiatric harm and / or illness, as well as physical injury.