Michelle Buckingham was found dead on the side of a rural road in Kialla East, just outside Shepparton, in November 1983. The 16-year-old was last seen more than two weeks earlier, walking down one of the town's main streets on Friday, October 21, 1983.

Stephen James Bradley, 53, has pleaded not guilty to her murder, but during the trial on Tuesday, admitted helping dispose of her body. Mr Bradley, who had been working as a dog groomer in Brisbane, was charged in March 2014 after his brother-in-law gave a statement to police during a reinvestigation into the teenager's death.

On Wednesday, the second day of the trial in the Supreme Court in Shepparton, Norm Gribble said Mr Bradley came to him in his green HQ Holden on a Saturday morning in 1983, sobbing and with blood on his hand.

"I asked him what the hell was going on," Mr Gribble told Crown prosecutor Andrew Tinney SC.

"He said, 'Can't talk about it'."

Mr Gribble told the court he took Mr Bradley, who continued to sob, for a drive to Waranga Basin, a picnic spot about 25 minutes from his home near Shepparton. He said the pair shared four stubbies of beer.

"That sort of calmed him down a bit," Mr Gribble said.

"He said, 'I've killed someone' ... I said 'f---ing bullshit' ... He said, 'We killed a girl last night'."

Mr Gribble said Mr Bradley told him he and two other men had picked the teenager up in his car from a caravan park where she had been staying and taken her to the back of the Pine Lodge pub in Kialla East, where they "put it on Michelle for sex".

Mr Bradley allegedly told Mr Gribble the teenager refused their advances and "they started to stab her", before putting her in the boot of his car and later dumping her body on the side of the road.

Mr Gribble said Mr Bradley refused to go to police for fear of repercussions from the other men. The trio had formed a pact that if they went down, they "went down together".

"They made a pact – 'We all had to stab her' – that way there was no come back," Mr Gribble said.

Under cross-examination, Mr Bradley's barrister, James Fitzgerald, suggested to Mr Gribble he had reconstructed the events from newspaper articles and his memory was "hazy".

He said his client never stabbed Michelle, nor did he make any sexual advances to her.

Mr Gribble rejected Mr Fitzgerald's suggestions, telling the jury "for years I've suffered – for years".

During his re-examination by the prosecution, Mr Gribble said he suffered because of "being told and being the only one that knew".

He said he was approached by Detective Senior Sergeant Ron Iddles in 2012 during a re-investigation into the matter, after Mr Bradley's brother, Lawrence Bradley, had spoken to the detective.

Earlier on Wednesday, a man who delivered fuel to farmers in the area told the court that twice on November 4, 1983, he had seen a green car near where Michelle's body was found  by a passing farmer three days later.

He said the same car had come to his depot for fuel and a girl he believed was Michelle Buckingham was in the car with another girl and two men.

The trial before Justice Robert Osborn continues.