The two elements of a criminal offence
For a criminal offence to occur there must be two main elements - the prohibited conduct and the mental element of a guilty mind or intention. Unless an offence falls into the unusual category of a strict liability offence, the prosecution must, in order to prove that a person has committed an offence, show that both these elements were present.
For example, if a person intentionally and without lawful excuse (such as self defence) strikes another without that person's consent, an assault has been committed. The prohibited conduct is the striking and the mental element, or guilty mind, is the intention to strike/hurt/injure.
On the other hand, if a person accidentally strikes another, no criminal offence occurs because the mental element, or guilty mind, is absent. However, sometimes a person may commit an offence by acting recklessly, that is, without a specific intent but disregarding or not caring about the consequences of their actions.
Strict liability offences
Strict liability offences are the exception to this rule and require only the commission of the prohibited conduct for an offence to arise. That is, no mental element is required. Strict liability offences are usually offences of a relatively minor regulatory nature.
For example, many offences against the Public and Environmental Health Act 1987 are strict liability offences. An offence is committed if a shop is unclean, whether or not the proprietor intended the premises to be unclean. Similarly, if a driver is speeding, the prosecution does not need to show that the driver also had a guilty mind or intended to travel at that speed. As this is a strict liability offence, the mere fact of travelling at a prohibited speed is enough to make it an offence. It is not a defence that the vehicle's speedometer was faulty or that the driver thought she or he was driving within the speed limit.
Ancillary criminal responsibility
Most people charged with offences are principal offender. In general terms, a principal offender is a person who performs prohibited conduct, but a person who is less directly involved with that conduct can also have criminal responsibility on the basis of 'joint enterprise'. The person who drives the getaway car is just as guilty as those who hold up the bank, the person who keeps a lookout is just as guilty as those who break into the house and steal property as long as that person is aware of the offence that the offender is committing.
An offence can be committed by a person who promotes, aids and abets, or conspires to commit, an offence. Those who encourage or give aid for the offence are known as accessories to the crime. It is also an offence to comfort or assist a person after an offence has been committed [Criminal Law Consolidation Act 1935 ss.241,267].
A person who does not manage to complete the offence can still be found guilty of attempting to commit the offence [Criminal Law Consolidation Act 1935 s.270A(1)]. A person can be charged with attempting to commit an offence or may be found guilty of attempt as a result of a case in which the person was charged with a completed offence but where, according to the evidence, she or he failed to complete the offence.
People who plan to commit a crime can be found guilty of conspiracy even where there has been no attempt made. People may be charged with this offence if there is evidence that more than one person planned a crime and there was an agreement to commit a particular crime. For example, if more than one person planned to rob a bank, they can be charged with conspiracy even if the bank had not been selected.