Driver, Graham Lees, 58, died and 28 of his passengers were injured after the bus careered out of control and crossed to the wrong side of Moss Vale Road on Barrengarry Mountain on May 14, 2010.

Mr Lees, the proprietor of the bus company G&S Minibuses Bringelly, yelled at his passengers to “brace yourself!” as the vehicle crashed through a metal road barrier and 40 metres down a steep embankment, coming to rest in dense bushland.

A subsequent police investigation found the rear brakes on the bus had catastrophically failed.

Court documents reveal the bus failed its mandatory bi-annual inspection on May 3, 2010, resulting in operations manager Simon Lees, the son of the victim, having the the company’s in-house mechanic work on it.

It is alleged the mechanic adjusted the rear brake units instead of replacing them, leaving the brakes “in a decrepit and dangerously defective condition”.

Lees claims he then took the vehicle to Picton mechanic and authorised heavy vehicle inspector Stuart Lewry to approve the work. Lewry signed a declaration saying he had inspected the vehicle and was “satisfied ...the defects have been properly rectified”.

However, police will allege Lewry never inspected the bus and had simply signed off on its road worthiness after Lees assured him the problems had been fixed.

A witness allegedly overheard a phone conversation between Lees and a man identified as “Stuart”, in which Lees said “I’ve got a bus that’s just been defected, it needs to be cleared for tomorrow, we’ve adjusted the brakes and everything’s fixed, and it’s not a problem”.

Following an extensive investigation, police charged Lees and Lewry with a string of offences earlier this month, including manslaughter by criminal negligence, concealing a serious offence, publishing misleading material and perverting the course of justice.

Lewry appeared in Moss Vale court on Tuesday, where his lawyer said he would fight the charges.

“My client is of the view that … anything [he] did, or did not do, did not cause the fatal accident,” the lawyer said.

Lees will face the same court on April 18.