In the first day of a two-week trial in the country Victorian town, a lawyer for Stephen James Bradley told the jury his client pretended to stab Michelle Buckingham when he thought she was already dead and at the behest of her real killer, his friend Rodney Butler.

It's a contention rejected by the prosecution, whose case relies on a confession by Mr Bradley, 53, to his brother-in-law the morning after Michelle was murdered almost 32 years ago.

It was a confession unearthed when brother-in-law Norm Gribble came forward after a fresh investigation was launched by Detective Senior Sergeant Ron Iddles and his cold case team in 2012.

The court heard that most of the evidence – including photographs – were destroyed by police in 1994, the material labelled a "biological hazard" by an inspector.

Crown prosecutor Andrew Tinney, SC, told the jury that as a result, only 11 photographs of the crime scene, and the teenager's partly decomposed body, remained.

Mr Tinney told the Supreme Court they would rely on the evidence of a number of new witnesses, the most important of those "by far" being Mr Gribble.

He said a distressed Mr Bradley told Mr Gribble he, Mr Butler and another friend Trevor "Lurch" Corrigan had killed "a girl last night" after they had "put the hard word" on her behind a pub outside of town.

Mr Tinney said Mr Gribble was told Mr Butler, who has not been charged, stabbed Michelle first and told the others to stab her too.

Mr Tinney said Mr Bradley said "We all had to have a go at stabbing her so there was no one left to point the finger at".

Mr Bradley's barrister, James Fitzgerald, told the jury Mr Gribble's memory has "failed him" and that while he spoke with Mr Gribble about the incident, he never confessed to murder.

"He was guilty of a different offence, the offence of assisting the offender ..." Mr Fitzgerald said.

Mr Fitzgerald said that when Mr Butler asked Mr Bradley to stab Michelle, he thought she was already dead and he pretended to stab her.

The court heard Michelle's body was found two weeks later in long grass on November 7, 1983, beside a rural road in the vicinity of the Pine Lodge pub. She had sustained 19 stab wounds.

Michelle, who was working at Coles after leaving school, had moved out of home in the lead-up to her death after an argument with her mother. She was staying with a friend at the Strayleaves Caravan Park in Shepparton East.

She was last seen on October 21 outside a bowling alley by two friends, who she had stopped to ask for directions back to the caravan park.

She was reported missing about a week later by her father.

A statement from her mother, Elvira Buckingham, was read out to the jury by Mr Tinney.

Mrs Buckingham told Detective Senior Sergeant Iddles she did not know Mr Bradley, nor Mr Corrigan, but was "shocked" to learn of Mr Butler's alleged involvement.

"I know Rodney Butler, he was a friend of Michelle's," Mr Tinney read.

The trial before Justice Robert Osborn continues.