The murder of a Sydney woman weeks after her wedding that continues to baffle police.

On the evening of Monday, April 22, 1974, Maria Smith was found dead in her Sydney unit.

Forty-four years on, her widowed husband Stephen Smith is still hoping to find her killer.

Maria was just 20 years old and had only been married to Stephen for eight weeks when she was murdered. But despite how brief their time together was – Stephen and Maria met when she was 17 and he was about 19 – the pain of her loss still haunts the engineer, now aged in his 60s.

The tragic killing made headlines when it was first reported, in part due to the shocking nature of the crime: the newlywed had been raped, bound and strangled with her own tights.

Yet nothing ever came of police’s investigation. No one has been charged with her murder.

Now, four decades on, police have renewed calls for information about Maria’s death and upped the reward for any knowledge that leads to an arrest to $1 million.

New information in relation to the killer

Police may not have an identified person of interest, but they do have a potential motive for the crime, and a car they would like to meet the owner of.

In an interview with Fairfax, police revealed that Stephen had only recently shared more information with police about the week leading up to her murder and a car seen at their Randwick unit.

Detective Senior Constable Deon Kelly said that Maria, who was a trainee teacher but also worked part-time as a barperson at the Malabar RSL Club, had attended a party there the Friday before her death. After the RSL, the party had moved to a Randwick pub, then to the couple’s unit on St Marks Road.

Stephen, who was studying engineering at the time, had been at a film for university instead that night.

Detective Kelly said that night a man at the party had made advances on Maria and he had been firmly rejected.

Could a scorned suitor have killed Maria in a despicable act of revenge? Stephen thinks someone at the RSL may have been behind it.

"I have always assumed it [the murder] was associated with the Malabar, only because of the people that were there. There were some shady characters, that's the best way of describing it," he said.

Police aren't sure, and they haven't ruled out other potential suspects and unknown motives as alternative theories.

Homicide Squad Commander, Detective Superintendent Scott Cook, said in a statement last month that investigators at the time thought Maria's murder may have been linked to the slaying of another woman, Lynette White, around the same time.

"Having reviewed both cases, we are now conducting separate investigations into each of these matters," Det Supt Cook said.

"That said, we are keeping an open mind and welcome any information from the community that may assist our inquiries and help bring us closer to providing answers to both families.

"Investigators are seeking to re-interview various people who were in contact with Maria at the time, including friends, work colleagues, and even those she may have spoken to while working at Malabar RSL Club."

Stephen told Fairfax the couple had gone to another party together on the Saturday night where he'd "had too much to drink". Perhaps another man had spoken to Maria that night and began plotting an attack.

For police, one piece of the jigsaw puzzle is how the attacker got into the Smiths' unit.

Maria's estimated time of death was about 8.15am, about an hour after Stephen left for work and around the time she would catch a bus to get to work at Brigidine Convent School.

Neighbours said they heard no knocks at the door that morning. Police said there were no signs of forced entry.

However, Detective Kelly said there was a balcony that someone could have climbed to reach. Police say that door was locked when they arrived and that Stephen insisted he'd locked it before he left, but that doesn't mean it couldn't have been open at some point that morning.

Another key piece of information police are hoping might lead to an arrest is a car Stephen saw at his unit that he "hadn't seen there before". Police say it was a mustard-coloured Ford Capri.

'Void that can't be filled.'

Maria's brother Peter McGuinn said in a statement last month he hoped the $1 million reward might lead to new information and the eventual arrest of his sister's killer. Peter also described just how hard her loss had been on their family.

"From that day, it was like there’s a void that couldn’t – and can’t – be filled," he said.

"Even after 44 years, we still think about Maria often, mostly it’s our childhood memories and what could have been, but other times, I think about what actually happened – who killed my sister?

"Even though our parents have passed without that answer, we know that someone knows who did it and hope that this reward is encouragement to come forward and tell the police."

As for Stephen, he has remarried twice since and helped raise two "wonderful" boys he speaks to every few days.

But he still thinks of Maria and described how each milestone anniversary of her death was a disappointing reminder no one had been caught.

Now, he's feeling hopeful.

"I am assuming that somebody knows something. And they are not coming forward. Now's the time."

Police are urging anyone with information to phone Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page.