Which of the following is considered an aspect of an offence?

Mens rea is an essential aspect of an offence because it refers to the mental state or intention behind a person's actions at the time the offence is committed. In legal terms, mens rea translates to "guilty mind" and indicates that a person had the intention to commit a crime or was reckless in doing so. Understanding mens rea is crucial in determining the severity of the offence and in establishing culpability. Without mens rea, certain offences may not be prosecutable because the lawful basis of intent or knowledge is absent.

Justification, self-defence, and opportunity do not reflect the mental state required for an offence. Justification relates to the reasoning behind an action, such as whether it is warranted under the law. Self-defence is a legal argument used to justify actions taken in protection of oneself from harm, while opportunity pertains to the circumstances enabling someone to commit the offence, but none of these concepts directly capture the mental state of the offender as mens rea does.