A Cowra police officer who was rostered on at Orange police station says he faked a breath test to help a colleague's son dodge a drink-driving charge because he “felt sorry for him”.

Senior Constable Mark Christie told the Police Integrity Commission (PIC) yesterday he acted alone when he decided to protect Adam Clunes, the son of Leading Senior Constable Colin Clunes.

Mr Clunes, 19, blew 0.202 in a roadside test after being pulled over by police in Orange in the early hours of December 21 last year.

Snr Const Christie said he was the on-duty breath analysis service (BAS) operator at the station when Mr Clunes was brought in for further testing.

He told the commission he blew into the BAS machine instead of Mr Clunes, but said it had nothing to do with Snr Const Clunes.

He said it was the first time he falsified a breath test in 10 years as an officer.

However, he said his perspective on life changed after he was assaulted by a prisoner and suffered concussion just days before Mr Clunes' arrest.

“I began to feel very much different about life,” Snr Const Christie said.

He said his actions were “something that arose in me that night”, and the thought to blow into the BAS machine himself and fake the result was spontaneous.

“The young fellow was in great peril of losing his licence, his job, his career,” Snr Const Christie said. “I felt great empathy for that.”

Snr Const Christie apologised to the PIC for his actions and the disgrace he had brought on his colleagues and the NSW Police Force.

“I acted alone. I haven’t needed to collude with other police. It was a poor decision made on the night,” he said.

He told the inquiry he was suffering from a stress condition and arresting officer Constable Kate Lanser was “hysterical” when she brought Mr Clunes in, due to his father being a senior colleague.

Const Lanser earlier told the inquiry Snr Const Clunes was very upset in phone conversations she had with him following his son's arrest.

She said she felt he implied she should not charge Mr Clunes because he would lose his licence and possibly his job.

Phone records tendered at the inquiry showed eight calls between Const Lanser and Snr Const Clunes in the hour between Mr Clunes’ arrest and when he was released.

Snr Const Clunes told the commission he expected his colleagues to follow standard procedure, but admitted he may have asked Const Lanser to “do something”.

But he said the last thing he told Const Lanser was “do what you've got to do”, meaning follow correct processes.