An 'arrest' is where a person is detained by another and is not free to leave.
Do police have to have a warrant to make an arrest?
The police can arrest someone either with or without a warrant and the majority of arrests are made without a warrant. Alternatively, the police can choose to issue a summons for a person to appear in court rather than arrest them.
What is a warrant?
A warrant for a person's arrest is a written authority from a magistrate or judge for the arrest of a named person. It authorises all police officers to arrest the person named whenever that person is found. It can be issued for an offence or for failing to attend court at a nominated time.
A person arrested on a warrant is taken into custody and must be brought before a court. The person does not have to be taken to court if the warrant includes an order indicating that bail can be granted by the police [Criminal Procedure Act 1921 (SA) ss 20 and 69].
When can police make an arrest without a warrant?
Under the Summary Offences Act 1953 (SA), the police can arrest someone without a warrant who:
- is caught committing an offence [s 75]
- is reasonably suspected of committing an offence or is about to be commit an offence [s 75]
- is suspected of having an outstanding warrant 
- is suspected of having committed an offence interstate (which would be an indictable offence or an offence punishable by up to two years imprisonment had it been committed in South Australia) [s 78A]
Other South Australian state laws also give police the power to arrest someone without a warrant who:
- enters or attempts to enter a licensed premises after being removed by a license. A licensee can demand that a person leave immediately if they are intoxicated and their behaviour is impaired as a result and they are behaving in an offensive and disorderly manner [Liquor Licensing Act (SA) s 124(5)]
- is a defendant to an intervention order [Intervention Orders (Prevention of Abuse) Act 2009 (SA) ss 34-36]
- is a defendant to a restraining order not yet served [Criminal Procedure Act 1921 (SA) s 99E]
- is suspected of having committed a serious and continuing breach of parole [Correctional Services Act 1982 (SA) s 79B]
Under Commonwealth laws, the police can also arrest someone without a warrant who:
- is reasonably suspected of committing an offence under a Commonwealth law and a charge could not effectively be dealt with by summons [Crimes Act 1914 (Cth) s 3W]
- is believed, on reasonable grounds, to be involved in an offence such as smuggling or importing/exporting prohibited goods – this power extends to both police and customs officers [Customs Act 1901 (Cth) s 210]
What procedure must be followed if a person is arrested without a warrant?
People apprehended without a warrant must be delivered to the nearest police station as soon as possible [Summary Offences Act 1953 s 78(1)].
However, a person arrested without a warrant who is suspected of committing an indictable offence or an offence punishable by imprisonment of two years of more, can be detained for as long as it takes to investigate the offence or the prescribed period, whichever is the less [s 78(2)]. The detention can be extended up to eight hours if authorised by a magistrate. During this time the person can be taken to places connected with suspected offences to assist police in their investigation [Summary Offences Act 1953 (SA) s 78].
For other particular types of arrest, such as arrest in relation to intervention orders or breach of parole, particular procedures must be followed. For example, see Parole.
Alternatives to arrest
Apart from arresting someone, the police can also ask a person behaving in a disorderly or offensive manner in a place of public entertainment to leave [Summary Offences Act 1953 (SA) s 73].
A person who is under the influence of alcohol in a public place such that they are unable to take proper care of him or herself may be taken to a sobering up centre or police station before being released. This is not an arrest [Public Intoxication Act 1984 (SA) s 7].