Senior police in Perth say there is no evidence to suggest officers intended any malice when they became involved in a melee with three members of the one family.

The Walker family were celebrating at a Perth nightclub in January when their son become involved in an altercation with police.

Ryan was tasered and his mother Raelene received a broken ankle.

Yesterday, a Perth court dismissed charges of assault and obstructing a public officer after the family's lawyer successfully argued CCTV footage of the incident did not support the police version of events.

Acting Assistant Police Commissioner Gary Budge says the officers involved genuinely felt a crime had been committed.

"The police officer who made an arrest that night was certainly of the belief he'd been assaulted by the person who had been charged," he said.

"We're certainly not in possession of any evidence to suggest any malice in his actions on that night."

Earlier, he told the ABC that CCTV cameras ensure accountability.

"If police officers are doing the wrong thing, they're going to be caught out, they're going to have to pay whatever penalty there is for doing the wrong thing, acting inappropriately or unethically or any other terminology you want to put on it.

Acting Assistant Commissioner Budge says an internal investigation will be conducted.

"This matter certainly causes some concern. We'll certainly be looking at our procedures and processes to determine why we didn't determine earlier if there were weaknesses in this prosecution."

Not the end

Ken Walker says the court throwing out the charges is not the end of the matter and the family will lodge a formal complaint against police.

"We'd love an apology," he said.

"I would think that would be the least that we should get from the police department."

The family is seeking thousands of dollars to cover court costs.

Opposition MP John Quigley says the case highlights the need to introduce taser guns with cameras attached to them.

"With the CCC being so strong in its recommendation that all the taser guns should have cameras on top of them, the commissioner is strenuously opposing them and so is Rob Johnson (Police Minister) for no good reason other than to cover up what's going on," he said.