Judy Dick (left) and Elizabeth Zeschner in an RCMP handout. (CP file photo)

Robert Bonisteel has been found guilty of first-degree murder in the deaths of two 14-year-old girls who were attacked while walking to a convenience store in East Vancouver three decades ago.

A B.C. Supreme Court jury deliberated for three days before returning to the Vancouver courtroom on Saturday with the verdict for Bonisteel, 57. He faces an automatic sentence of life in prison with no possibility of parole for 25 years.

Bonisteel was arrested in October 2002, 27 years after the snow-covered bodies of Judy Dick and Elizabeth Zeschner were found in Richmond in February 1975. The girls, who were best friends, had been stabbed to death.

The Crown used a taped confession from 2002 and DNA evidence gathered at the time of the crime, before DNA testing was used, in making its case.

Bonisteel's lawyers had argued that the confession was coerced and the DNA evidence was unreliable.

In the videotaped confession made to police undercover agents, Bonisteel described in gruesome detail how he picked the girls up in his car, killed them with a knife and hid their bodies in long grass in Richmond, near Vancouver.

The DNA evidence was a trace of Dick's blood on Bonisteel's shoe.

Some members of the Zeschner family sobbed as the jury read its decision.

The family had Crown Counsel Hank Reiner read a prepared statement after Bonisteel was led away. The statement said they have been sentenced to a lifetime of unimaginable grief.

Bonisteel had fled to Winnipeg after the attacks. He was jailed for 20 years for two rapes he committed after leaving Vancouver.

RCMP Cpl. Peter Thiessen said before the trial that the police investigation hit a dead end years ago, but was reopened in 2002 thanks to advances in DNA collection and analysis.

"New technology played a key role," he said. "Being able to use that technology, going back to old evidence that was obtained back then, that was still accessible to the investigators, helped."