An arrest is valid if words such as 'you are under arrest' are used while at the same time touching or taking hold of the arrested person so that it is clear that he or she is being arrested.

However the police do not need to use these words to arrest someone. They ought to inform a person why they are under arrest and a person can be under arrest even if they are not touched, if the effect of the police action is to stop a person from doing what he or she wants. An arrest is only valid if the police reasonably suspect a person of committing an offence.

Most importantly, the person should be told of the right to remain silent, to have a friend or relative told of their arrest and to speak to a lawyer and have an interpreter present if required.

The person should also be told the reason for the arrest, even if it appears obvious from the circumstances, although the omission of this information does not necessarily make the arrest unlawful. However a court has a discretion to exclude evidence flowing from the arrest (such as a record of interview), where it would be unfair to the suspect to use it, or where for public policy reasons the court excludes the evidence.

Generally an arrest will be lawful if the officer who carries it out is acting as a result of an honest and reasonable belief in the relevant facts. The arresting party may be mistaken as to the facts, and the person later released. Provided, however, the person had an honest and reasonable belief in the relevant facts, then the officer has acted lawfully. For that reason no attempt should ever be made to resist arrest. Civil action can however be taken for damages or compensation if a wrongful arrest is made.

A police officer may use as much force as is reasonably necessary to arrest the person. Unreasonable force is assault. It is up to the court to decide whether the force used was reasonable in the circumstances. For example, force that is likely to kill or cause grievous bodily harm has been held reasonable if the person could not be arrested in any other way [R v. Turner (1962) VR 30]. Handcuffs or a similar restraint are reasonable force where the person has physically resisted arrest or attempted to run away.

It is an offence to resist or hinder a police officer in the execution of his or her duty - including the making of a lawful arrest [Summary Offences Act 1953 s 6]. The resistance to the arrest must be active. Merely lying down and refusing to co-operate is not resisting nor is running away from a police officer before a valid arrest. A person can hinder the police by passive actions that render a police action more difficult, but not impossible.

A person innocent of any other offence can nevertheless be charged with resisting arrest or hindering police in the execution of their duty. The police are entitled to proceed with a charge of resist arrest or hinder even if the evidence later suggests that the original offence that the person was arrested for should not proceed. The exception to this is where the arresting person knew or suspected there was no offence being committed.