Matthew Donald Tilley, 49, had been on trial in the South Australian Supreme Court over the 1993 stabbing of Suzanne Poll.
Poll, 36, was found in the rear of a stationery store in Salisbury where she worked, with at least 18 separate wounds.
After deliberating for more than four hours, a jury returned its guilty verdict on Thursday night.
Opening the crown case last month, prosecutor Carmen Matteo said improvements in DNA techniques ultimately resulted in Tilley being charged.
She said a DNA profile originally extracted from a man’s blood at the murder scene returned a familial match with Tilley’s brother in late 2017.
That ultimately led detectives to travel to Victoria to question the accused and after noticing him discard a disposable coffee cup, they retrieved it and brought it back to Adelaide for testing.
That returned a match with a further test after Tilley was arrested in 2019.
Matteo said an autopsy conducted on Poll’s body found that she died from massive blood loss following the attack in the store.
On the prosecution case, she was killed by a man who entered close to closing time.
In Tilley’s defence, his lawyer argued that a key question for the court was whether the evidence had been properly preserved over almost three decades.
After the guilty verdict, Justice David Peek imposed the mandatory head sentence of life in prison.
A future court hearing will set a non-parole-period.
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