No witnesses saw anyone who looked like the accused killer at the scene of an Adelaide cold case murder, and prosecutors need to prove the evidence hasn't been contaminated over the past 30 years, his lawyer has told the court.
Matthew Donald Tilley, 48, is on trial accused of murdering Suzanne Poll in the Salisbury stationery shop where the 36-year-old worked in 1993.
During the trial, the jury has heard Mrs Poll was killed in a "ferocious" manner with a knife while she worked alone near closing time on late-night shopping.
Prosecutor Carmen Matteo told the jury that blood samples taken from the scene were decades-later matched to Mr Tilley and he was arrested in September last year.
But Mr Tilley's lawyer, Jane Abbey, told the jury the amount of Mr Tilley's blood found at the scene was equivalent to a "vial of blood" but Mr Tilley had no visible cuts or injuries to his hands at the time.
"There's not."
Ms Abbey said the jury was required to prove beyond reasonable doubt that Mr Tilley's blood was at the scene "because he is the killer".
She told the jury the prosecution also had to exclude the risk of DNA and evidence contamination "somewhere along the way", in the nearly three decades before Mr Tilley was charged.
"You can't exclude, I suggest, the risk that there has been a contamination which has affected those results," she told the jury.
"It is not a question of me having to prove to you that the chain is broken; it's a question of the prosecution having to exclude that it's broken.
"Trying to prove something about which there are no records is … impossible, isn't it?
"We know that there has been multiple re-samples over time."
She told the jury none of the fingerprints or palm prints taken from the scene matched Mr Tilley's.
She said there were several examples where "ordinary practice had been departed from" and where records lacked.
"This trial has shown us that we cannot assume that general procedure was followed," Ms Abbey said.
She told the jury that video footage — taken by media outlets at the time — showed crime scene investigators did not all wear protective overalls, foot protection or gloves to prevent contamination of the scene.
Ms Abbey said contamination of evidence could be caused by a contaminant, a mislabelling or a mistake.
Mr Tilley was working at a service station at the time of Mrs Poll's murder but the court heard records no longer existed to ascertain whether he was working that night.
Witness descriptions don't match the accused, lawyer says
Ms Abbey also told the jury witness descriptions of men hanging around the shop prior to the murder "did not fit the description of Mr Tilley" at the time.
"You might think this is a case where there's no evidence of a sighting of Mr Tilley, or someone who looks like him," she said.
She also said there was "a bit of a theme" of "honestly mistaken witnesses" in the trial.
"Honestly mistaken witnesses can be the most dangerous kind," she told the jury.
She told the jury Mr Tilley had reiterated during a prison phone call that he had not committed the crime.
Mr Tilley did not take the stand in his defence but Ms Abbey said "everyone has a right to silence" and that was not to be used as evidence against him.
The trial continues.
