Gay Williams says she knew within a week of her daughter's death that the 18-year-old's husband was responsible.
After a 20-year wait for justice, on Tuesday Ms Williams felt relief after a NSW Supreme Court jury found Steve Frank Fesus guilty of her daughter Jodie Fesus' murder.
The 46-year-old had pleaded not guilty to murdering his teenage wife in August 1997 at their Shellharbour home before burying her body in a shallow grave at Seven Mile Beach, near Gerroa.
He didn't react when the 11-person jury found him guilty on Tuesday afternoon after less than a day of deliberations.
But members of his wife's family gasped and cried.
Ms Williams said it was a bittersweet moment that gave her family "some satisfaction that the justice system does eventually work".
"We've known for 20 years, it's just one of those things, we had to wait for justice to prevail," she told reporters outside court.
"We knew within the first week that he was guilty but couldn't prove it.
“Now it's been proven to the world."
During the trial the jury heard an anonymous man rang police from a public phone on September 14, 1997, a month after the teenager's disappearance, giving directions to locate human remains at Gerroa.
Before the discovery of her body, Fesus applied for a pension on a form where a question asking if his wife was still alive had been changed from "no" to "yes" - an amendment he initialled.
He couldn't get a pension while his wife was missing but was approved for one after her body was found, the court heard.
The Crown argued Fesus was financially motivated to return to the beach to uncover the body so it would be discovered.
His barrister, Keith Chapple SC, argued he had nothing to do with such an "incredibly risky, foolhardy idea that he could go and bring on the discovery of the body".
Fesus was remanded in custody after Tuesday's verdict.
He is expected to return to court on December 15 for a sentencing hearing.
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