A $1 million reward has been offered for information that leads to a conviction in the case of a young teacher found raped a strangled in her Sydney home four decades ago.
The body of Maria Smith, 20, was found by her husband in the bedroom of their Randwick unit on April 22, 1974.
"Maria was horribly murdered," the head of the NSW homicide squad, Detective Superintendent Scott Cook, told reporters on Tuesday.
"She was bound, gagged and sexually assaulted before being strangled."
It is only the second time in the state's history a $1 million reward has been put on the table, matching the same sum that remains on offer in the case of missing toddler William Tyrrell.
Despite extensive investigations over the years, no one was charged with Ms Smith's murder.
Her brother Peter McGuinn, who was 22 at the time, recalled clearly the afternoon when Steve Smith discovered his wife's body.
"I remember a home that was just devastated," he said at the announcement.
"Our family was just in total shock. We had people around us to support us, but it was a bloody nightmare."
Mr McGuinn said the entire family had been affected and many had become overly cautious for years after.
He was encouraged by the reward and said every few days or months his sister came into his mind.
"You never put a tragedy like this to bed."
Det Supt Cook said police are particularly eager to speak with anyone who lived in the unit block at 14-20 St Marks Road, Randwick in early 1974, regardless of whether they've previously been interviewed.
The reward comes as NSW Police announced on Monday about 500 cold case homicides dating back four decades would be reopened and re-examined with fresh eyes and cutting-edge technology as police attempt to catch the killers.
Specialist detectives from across the force will conduct formal case reviews.
The request for "fresh eyes" to examine the cases came from victims' families, police said.