Matthew has been charged with assault. His victim, John, was an annoying man with whom Matthew frequently argued. John had a habit of sitting in his back garden listening to Radio 4 at a level which, while not excessive, was sufficient to irritate Matthew. One day, Matthew feels he has had enough of being forced to listen to Radio 4 from the other side of the fence. He dons a balaclava and rushes down the side of the house and into John’s garden, brandishing his son’s toy gun and shouting incoherently.
John is naturally extremely alarmed by this, as is the old lady who lives on the other side of John, who witnesses this from her bedroom window. She phones for the police who arrive to find John in a state of shock, and the replica gun (complete with fingerprints) lying on the patio. On questioning John, it is clear that he thought the gun was real. On being questioned, Matthew admits that it was him, but asserts that he only meant to get John to turn down the radio, and had thought it would be a bit of a joke. Advise Matthew on the likely outcome of the case against him.
You should not make reference to the law on assault, but focus on the mental element of crime which we have already covered in class. The issue in this case is whether Matthew’s admitted actions, which were carried out as a joke, would constitute as a relevant defence to the charge of assault held against him. The general rule is that before a person can be convicted of a criminal offence it must be shown that the alleged offender committed an act or omission proscribed by the criminal law at the time that the alleged crime or offence was committed. This wrongful act is usually expressed as the actus reus.
An actus reus can consist of more than just an act, it comprises all the elements of the offence other than the state of mind of the defendant.  Along with this requirement it is essential that the conduct of the act be accompanied by a guilty state of mind, also known as the mens rea. When establishing the mens rea of the crime it is important to take a subjective approach to determine what the accused was thinking at that time. On considering the actus reus of the crime within this case it is required that the act shows that the accused is capable of causing actual harm to society and that is prohibited under the criminal law.
 It is evident from the facts of the case that Matthew was in conscious control of his actions as he had the power to stop what he was doing. This is regarded as a voluntary act. The actus reus in this situation is the wrongful act of assault. This could be established when the case describes Matthew brandishing the toy gun and shouting incoherently. It could be said that Matthew could be capable of causing harm to society because it was unbeknown to the other parties in the situation that the gun was only a toy. However, for Matthew to be criminally liable for the conviction of assault a guilty state of mind must be established.