What Is The Law Around Making A Citizen's Arrest?

All states and territories have legislation allowing for civilians to perform citizen's arrests, but how can you protect yourself from ending up on the wrong side of the law as well?

Brave passengers performed a citizen's arrest on a man allegedly assaulting a Brisbane bus driver on Thursday afternoon.

A 19-year-old man allegedly head-butted and punched the driver after he was ordered off the bus during a verbal dispute at Bracken Bridge in Brisbane.

The man was restrained by passengers until police arrived, and he has been charged with occasioning bodily harm.

The driver was left with facial injuries and taken to hospital for treatment.

But What Are Legalities Behind Performing A Citizen's Arrest?

A citizen's arrest can only be made if a person has witnessed a crime taking place, Professor Murray Lee, from the University of Sydney Law School, told 10 daily.

"Where it can go wrong is if someone tries to arrest someone because they think they're about to commit a crime," said Lee, a Professor of Criminology.

"Ultimately, you have to know a crime has been committed."

Referring to the alleged incident in Brisbane, Lee said had the passengers only believed the passenger was going to commit a crime, they would not have had legal grounds to perform a citizen's arrest.

"That wouldn't have been enough, it would have been illegal for them to make an arrest in that case,' he said.

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Another area people can get themselves into trouble is the force used in a citizen's arrest.

"You can't use excessive force, only use the force necessary to restrain the person," Lee said.

"If they think 'I'm defending my property, I'll use whatever force I think necessary', well that's not legal."