Police Powers, Trespass and Malicious Prosecution: Cosenza v State of South Australia
The Court of Appeal in Cosenza v State of South Australia [2026] SASCA 49 discusses the limits of police powers, private property rights, arrest warrants, and malicious prosecution.
Police powers and private rights
The case arose from events in 2015, when Mr Dean Cosenza was arrested after refusing an alcotest, later charged, and then arrested again under a warrant with a “no bail” endorsement. The original charge was ultimately withdrawn in 2016, largely on public interest grounds.
Mr Cosenza later brought civil proceedings against the State of South Australia, alleging several wrongs by police, including unlawful arrest, false imprisonment, malicious prosecution, misfeasance in public office and trespass.
The result was mixed: Mr Cosenza succeeded on part of his malicious prosecution claim, but the State succeeded in overturning the earlier trespass damages award.
The background
On Good Friday in 2015, a SAPOL officer observed Mr Cosenza driving erratically. The officer required him to submit to an alcotest. Mr Cosenza refused and became aggressive. The officer arrested him for failing to comply with the alcotest requirement, but then “unarrested” him after Mr Cosenza appeared to suffer a medical episode.
Mr Cosenza was taken to hospital, where a blood sample showed a blood alcohol level of 0.011 per cent, well below the legal limit.
Despite that, he was charged with refusing to submit to an alcotest. Police later made several unsuccessful attempts to serve him with a summons at the Woodville South property where he lived with his mother. A police prosecutor then applied for a warrant for his arrest, with a “no bail” endorsement. That meant police could not release him on bail after arrest; he had to remain in custody until brought before court.
Mr Cosenza was arrested on 30 August 2015 and kept in custody overnight before being granted bail the next morning.
What did the Court of Appeal decide?
The Court of Appeal made two key findings.
First, the Court found that Mr Cosenza’s claim for malicious prosecution was established in part. This related specifically to the police prosecutor applying for an arrest warrant with a “no bail” endorsement. The Court found that the application was made without reasonable and probable cause and for an improper purpose. The assessment of damages for that arrest and overnight detention was sent back to the General Division of the Supreme Court.
Second, the Court allowed the State’s cross-appeal on trespass. The earlier award of $40,000 plus interest for trespass was set aside. The Court found that Mr Cosenza did not have standing to bring the trespass claim because he did not have possession of the Woodville South property in the legal sense required. He lived there under a licence or lodging arrangement with his mother, who was the registered proprietor. Further, that he had not effectively communicated that the police’s implied licence had been revoked.
The formal outcome was that the appeal was allowed in part, the State’s cross-appeal was allowed, the trespass damages were set aside, and the malicious prosecution claim was established only in the narrower respect concerning the arrest warrant and “no bail” endorsement.
Why the “no bail” warrant mattered
One of the most important parts of the decision concerns the use of a “no bail” endorsement.
The Court found there was no reasonable and probable cause for seeking an arrest warrant with a “no bail” endorsement in the circumstances. The original charge was not punishable by imprisonment, there was no proper basis to treat Mr Cosenza as a flight risk, and the likely consequence was that he would be held in custody overnight or longer.
The Court accepted that the relevant police prosecutor acted with malice — in plain English, for an improper purpose — by seeking the warrant to punish Mr Cosenza for being difficult or, as recorded in the judgment, a “pain in the arse”.
That finding is significant because it confirms that the legal system cannot be used as a punishment mechanism. Arrest powers and bail restrictions must be used for proper legal purposes, not personal frustration or animosity.
What is malicious prosecution?
Malicious prosecution is a civil claim that may arise where someone improperly uses the legal process against another person.
In simple terms, a person claiming malicious prosecution usually needs to show that:
legal proceedings were brought or used against them;
the relevant proceedings ended in their favour;
there was no reasonable and probable cause;
the person responsible acted with malice or an improper purpose;
and the claimant suffered loss.
This case is particularly interesting because the successful claim was not about the whole prosecution from start to finish. It was narrower. It focused on the step of applying for an arrest warrant with a “no bail” endorsement.
The Court accepted that maliciously procuring an arrest warrant without reasonable and probable cause can found a claim similar to malicious prosecution.
What about the police trespass claim?
At trial, Mr Cosenza had succeeded on his claim that police trespassed when they entered the Woodville South property to try to serve a summons. The trial judge awarded him damages for those trespasses.
However, the Court of Appeal overturned that finding.
There were two main reasons.
1. Mr Cosenza did not have the required possessory interest
Trespass to land is about interference with possession of land. The Court found that Mr Cosenza’s mother owned and occupied the property, and that Mr Cosenza lived there with her permission under an informal licence or lodging arrangement.
That was not enough to give him standing to sue for trespass in his own name.
2. The police officers had not personally been told their licence to enter was revoked
The Court also considered the issue of implied licence.
Ordinarily, members of the public — including police in some circumstances — have an implied licence to walk up a path or driveway to a front door for a lawful purpose, such as knocking, delivering documents or making an enquiry.
That implied licence can be revoked. However, the revocation must be effectively communicated to the person entering, or be so clear that a reasonable person in their position would understand they were not permitted to enter.
In this case, the sign at the property was found to be too small and poorly positioned to effectively communicate refusal of entry. The officers also did not personally know about Mr Cosenza’s earlier correspondence to SAPOL purporting to revoke the implied licence.
Because of that, the trespass claim failed.
Does a “No Trespassing” sign stop police entering your property?
Not always.
This case confirms that a sign may be relevant, but it needs to be clear in both visibility and content. A small or poorly placed sign may not be enough.
Also, a sign does not override lawful police powers. Police may still be able to enter private property where they have:
a search warrant;
an arrest warrant;
statutory authority;
emergency grounds;
or another lawful basis.
But if police are relying only on the ordinary implied licence to come to the door, a clearly communicated revocation may matter.
What does this case teach the public?
This case is a useful reminder that police powers are important, but not unlimited.
It also shows that civil claims against the State can be complicated. A person may succeed on one legal issue but fail on another.
In this case:
the roadside arrest was not found to be unlawful;
the execution of the arrest warrant was not treated as false imprisonment by the officers who executed it;
the broader prosecution claim failed;
the narrower malicious prosecution claim about the “no bail” warrant succeeded;
and the trespass damages were overturned.
That mixed result is important. It shows how carefully courts separate each legal issue.
Why this case matters
Cosenza is a strong case to study because it covers several major legal concepts in one judgment, including:
false imprisonment;
trespass to the person;
trespass to land;
implied licence to enter property;
malicious prosecution;
misfeasance in public office;
police powers of arrest;
arrest warrants;
and State liability for police conduct.
It also shows the difference between conduct that may feel unfair and conduct that is legally actionable.
A reminder about accountability and lawful process
Cosenza v State of South Australia is a reminder that the justice system must be used carefully and fairly.
Police and prosecutors have important public functions. But powers of arrest, warrants and bail restrictions must be used for proper legal purposes — not to punish a person for being difficult, frustrating or inconvenient.
If you are concerned about police conduct or the use of legal process against you, it is important to get advice early.
This OYBlog was created with AI assistance based on the following source:
Cosenza v State of South Australia [2026] SASCA 49