NSW jail security boss at corruption probe

A former manager of security at a NSW jail is due to appear before a corruption inquiry over allegations guards colluded to cover up the bashing of an inmate.

Several officers are accused of using unwarranted force on the inmate in his cell at the Lithgow Correctional Centre in February 2014.

Brad Peebles, who is alleged to have been complicit in a plot to lie on official reports about the incident, is expected to be called before a NSW Independent Commission Against Corruption hearing in Sydney on Thursday.

Mr Peebles has been stood aside during the two-week probe, however until weeks ago he was one of the department's most senior officials.

The inmate suffered injuries including a black eye, bruising to the mouth and injured ribs after he was allegedly bashed by a specially-trained squad who thought he'd been abusive over an intercom.

Official reports said he tripped and fell on a toilet while trying to flush contraband.

According to ex-senior officer Terrence Walker, who gave evidence last week, Mr Peebles urged a clean-up because "this one will come back to bite us on the arse".

The jail's former intelligence manager Brian McMurtrie on Wednesday admitted he manufactured a reason for the guards' visit - a tip-off the prisoner had buprenorphine.

When asked why he lied, he said: "It's a question I still ask myself, to be honest".

Mr McMurtrie said initially he didn't know about the alleged bashing and thought he was simply giving a reason for the officers to be in the cell.

He later heard a recorded phone call between the inmate and his father in which the man said officers "flogged the f*** out of me".

Mr McMurtrie said inmates often said things that weren't true over the phone, but conceded he conducted no investigations.