Crimes Act 1961, s 315 Bail Act 2000, s 37

The police can arrest you if:

• they find you committing an offence punishable by a prison term (or they’ve got good reason to suspect this), or
• they find you “disturbing the peace” (or they’ve got good reason to suspect this), or
• it’s a situation where they’ve got a specific legal power to arrest you (see below for examples), or
• they have a warrant for your arrest issued by a court – these can be issued for a range of reasons, including if you’ve breached a bail condition, or if you didn’t turn up at court when you were supposed to.

New Zealand Bill of Rights Act 1990, s 22

Note: Most arrests happen without a warrant. However, not all arrests can be made without a warrant. For some offences, legislation restricts police powers to make an arrest without a warrant. Even if police have the power to arrest you, they often have a discretion as to whether or not to actually do so. The police should always consider whether arrest is strictly necessary in the circumstances; if they don’t, the arrest may be considered unlawful or arbitrary.

These are some of the powers the police have under specific Acts to arrest a person without a warrant:

Summary Offences Act 1981, ss 39(1), 39(2)

• Minor offences in the Summary Offences Act 1981 – A police officer can arrest you if they’ve got good reason to suspect you’ve committed an offence against the Summary Offences Act. This Act deals with a range of less serious crimes like common assault, tagging, disorderly behaviour, and drinking in public (see: “Common Crimes”).

Family Violence Act 2018, s 113

• Breaching a family violence Protection Order – The police can arrest a person they have good cause to suspect has breached a Protection Order (see: “Breaches of Protection Orders: When the other person doesn’t obey the order”).

Policing Act 2008, s 36

• Drunk in a public place or when trespassing – If the police find you drunk in a public place, or drunk while trespassing on private property, they can take you into police custody. They have to release you once you’ve sobered up, and can’t hold you for more than 12 hours unless a health practitioner recommends to do so.

Mental Health (Compulsory Assessment and Treatment) Act 1992, s 109

• Mental illness – The police can take you into custody if you’re wandering in a public place, your actions give grounds for a reasonable belief that you are “mentally disordered”, and they believe that doing so would be in your interests or those of the public. They can take you to a police station, hospital, or other appropriate place and arrange for a mental health professional to examine you as soon as practical (see: Mental health).

Note: “Mentally disordered” and “mental disorder” have a specific definition in the Mental Health (Compulsory Assessment and Treatment) Act 1992 that is not necessarily the same as that used by medical professionals or members of the general public. In this Act, a “mental disorder… means an abnormal state of mind…, characterised by delusions, or by disorders of mood or perception or volition or cognition, of such a degree that it—
(a) poses a serious danger to the health or safety of that person or of others; or
(b) seriously diminishes the capacity of that person to take care of himself or herself”
Accordingly, the bar for the police being able to detain someone on mental health grounds is a high one. They cannot detain you simply because you seemed mildly depressed in a public place.