The trial in the cold case killing of Adelaide woman Suzanne Poll has heard a takeaway coffee cup proved crucial in the investigation.
Matthew Donald Tilley, 48, has gone on trial accused of Mrs Poll's murder in the Salisbury stationery shop where the 36-year-old worked in 1993.
A Supreme Court jury was told she was killed in a "ferocious" manner by a knife while she worked alone near closing time on late-night shopping.
Prosecutor Carmen Matteo said blood samples were taken from Mrs Poll's handbag and three spots around the store entrance.
She said by 1999, new technology had shown they belonged to a person dubbed "Unknown Male A", and by 2017, it had shown there was a family link to the defendant's brother.
South Australian detectives went to Daylesford in Western Victoria to obtain a sample from Mr Tilley.
"[A detective] pulled the coffee cup out of the bin, put it in an envelope and brought it back to South Australia."
A DNA sample was extracted from the lip of the cup.
When the "breakthrough" in DNA showed a match, Mr Tilley was arrested, and a more rigorous sample was taken.
Ms Matteo said the DNA in effect showed Mr Tilley was "billions" of times more likely to be the matching person than any other human.
The trial is expected to run for several weeks and hear from experts including detectives, crime scene investigators and forensic specialists.
Defence lawyer Jane Abbey told the jury to keep an open mind, as there was controversy around the identity of the killer and it still had to be proved in the court.
The trial continues.
