Final answer:
The actus reus for Section 20 GBH is unlawfully causing harm, which is carried out recklessly. It does not require proving an intention to cause serious harm, but the perpetrator must have foreseen the risk of harm and acted anyway.
Step-by-step explanation:
The actus reus for Section 20 GBH (Grievous Bodily Harm) under the Offences Against the Person Act 1861 is (a) Unlawfully causing harm. This means that for someone to be guilty under Section 20 GBH, they must have caused serious physical harm to another person without lawful excuse.
It's not necessary to prove that the accused intended to cause the serious harm, making it distinct from Section 18 GBH, which does require specific intent. However, the person must have committed the act that caused the harm recklessly, meaning that they foresaw the possibility of causing some harm but went ahead with the act anyway. Therefore, while the mens rea (mental element) for this offense includes recklessness, the actus reus is simply the unlawful act that causes harm.