The same officer then told another mate that he was planning to treat the commission's inquiry "with contempt", declaring "f--- you, I'll play your game".

The commission is investigating allegations that Corey Barker, 24, was assaulted at Ballina police station in northern NSW on January 14, 2011, after an altercation with police, and that officers then falsely accused the young man of assaulting them.

Under examination on Tuesday, Senior Constable Mark Woolvern was played a series of phone conversations he had with friends after the incident which were secretly recorded by the commission's investigators.

In one conversation, Senior Constable Woolvern is heard to say in reference to Mr Barker: "10 years ago, I would have just snotted him ... even five years ago...'

"I wouldn't have put up with this s--- ... I would have gone, 'you're not in charge, we are'."

When asked by counsel assisting the commission, Stephen Rushton, SC, what he had meant, Senior Constable Woolvern said, "I meant ... I might have just snapped, punched him..."

A number of weeks after the alleged attack on Mr Barker, Senior Constable Woolvern wrote a formal statement declaring that it was in fact Mr Barker who had assaulted police, a claim that he now admits was completely wrong.

Unlike a number of other Ballina police, Senior Constable Woolvern was not called to give evidence in the Ballina local court, a fact which he appeared to mention in two of the recorded phone calls with his friends.

"I got away with it, mate," he joked during one conversation.

In another conversation he said: "The good thing is I didn't give evidence in court ... happy days ... I'll just say "what evidence?"

Later in the same conversation, he declared that he would treat the commission with "contempt".

"I'm going to treat it with contempt ... f--- you, I'll play your game."

The hearing continues.