Over the years, we have seen many true crime stories that have gripped the nation.
But when it comes to Australia's most baffling crimes that remain unsolved, few are more mysterious than these six murders. Take a look back at them here.
When navy veteran Richard Dorrough killed himself, he left a suicide letter that came tantalisingly close to solving an enduring murder mystery.
Before his death, Dorrough, 37, had mailed his partner a parcel containing his computer, phone and an exercise book with the note that read: "I did kill three times… it's the hardest thing to live with."
Could it be that Dorrough was a man who'd got away with murder?
In 1997 he'd been questioned about the disappearance of 21-year-old Sara-Lee Davey, who he met on a night out in Port Broome, WA, in January while he was on shore leave.
The pair took a taxi to Dorrough's ship, HMAS Geelong, where he tried to bring Sara-Lee on board. Stopped by a fellow seaman, Dorrough told him he planned to get intimate with her and the duo walked out of sight.
Sara-Lee was never seen again.
Later that evening, a fisherman heard a woman scream, "What the hell are you doing? Get off me."
He also heard a splash – as if a stone had been thrown into water.
Sara-Lee's body was never found, but Dorrough was later seen with scratches on his face that had not been there before.
He was questioned by police but maintained Sara-Lee had not wanted to get intimate with him and disappeared.
A decade later, Sydney detectives matched Dorrough's DNA with a sample recovered from murdered prostitute Rachel Campbell.
Dorrough faced trial for Rachel's murder, but was acquitted.
While a coroner ruled Dorrough likely attacked Sara-Lee, there was no proof he killed her and her death remains a mystery. If Dorrough's note did indeed refer to the fact he murdered her and Rachel, the third victim remains unknown.
When Paula Barreau kissed her 12-year-old daughter Rhianna goodbye as she left for work she never thought that would be the last time she would see her alive.
It was October 1992. Rhianna was on school holidays and walked to a local newsagency at Reynella Shopping Centre in Adelaide to buy a Christmas card for an American penpal. She was later seen near Morphett Vale High School and at a junction 500 metres from her home.
When Paula got home at 4.10pm, the card was on the dining room table, the television was blaring and there was a discarded record on the living room floor. But there was no sign of Rhianna.
"I was hoping she was just at a friend's place and had forgotten what the time was - but that's not like her," Paula told Adelaide Now in 2015.
Chillingly, police revealed "suspicious activities" allegedly involving a Victorian-registered white Holden Torana spotted near where she was last seen, leading to fears she was abducted and murdered.
Despite a widespread search, the vehicle and its owner were never found, and Paula believes her daughter knew her killer – claiming Rhianna would have screamed "blue murder" had she been abducted by a stranger.
"My feeling is it was somebody she knew. That's what I can't understand," she said.
Millionaire haulage contractor Michael Griffey's decomposing body was found in a pool of dried blood on his garage floor in Pakenham, Victoria on January 2, 2006.
Michael, 45, was known for his generosity, but as detectives started to investigate the case, they learned he owed a $1 million in taxes and had also been having an affair for years. His wallet and mobile phone were missing, along with $1000 from his safe – and only three people knew the combination.
His wife Diane was the beneficiary of his $1.5 million life insurance policy, and police charged her with murder. But before the trial, Michael and Diane's 16-year-old daughter Cassandra dramatically confessed to killing her dad.
Diane's case was dropped but Cassandra was never charged as detectives didn't believe her story. In another twist, in October last year Michael's son Kenny, 30, broke a decade-long silence to deny he killed his father.
Michael's lover Gillian Gould, 55, who has since remarried and now runs a haulage company, claimed Diane knew she and the late millionaire were together.
"She [Diane] didn't want him, but she didn't want anyone else to have him," Gillian told the Herald Sun.
Michael's killer remains at large, despite interest falling on three separate family members.
The son of murdered Toowoomba mum Tamara Smith has called for a coronial inquest to investigate his mum's shocking murder.
It's been 17 years since the body of Tamara, 24, who was strangled, sexually assaulted with a beer bottle and had her left wrist slit, was found tied to a tree on a vacant lot in the Queensland town.
Police arrested her former partner Paul Templeton, alleging they found microscopic fragments of glass on his clothing matching the bottle.
After the jury failed to reach a unanimous verdict, Templeton was found guilty in a second trial and sentenced to life behind bars. However, a court of appeal later quashed the verdict.
Justice Catherine Holmes said the glass fragments – less than a quarter of a millimetre in size – were anything but conclusive. Semen was found on Tamara's underwear and a bloody fingerprint was discovered at the scene, but DNA didn't match Templeton's.
Tamara's son Brodie Bailey, now 23, wants a coronial inquiry so he can finally know the truth.
On January 13 2004, Susan Winburn failed to turn up to work, so her sister went to her home. She found Susan's naked and strangled body in the bathtub.
The Canberra public servant had been strangled but single Susan, 45, had no enemies. Described as a gentle person, it was said she couldn't bring herself to kill a spider if she found one in her home.
"She was a fun-loving person. Whenever she walked in a room she just lit it up," said her sister Catherine Castleman.
Police believe Susan was murdered when she disturbed a burglary at her home and "somebody in the Canberra community knows who did it".
Susan's purse was missing and a strange man had been spotted near her home.
It was believed the killer had placed Susan in the bath to wash off any traces of DNA.
At an inquest five years later, Chief Coronor Ron Cahill heard from police that there were four persons of interest in the case.
However, he said there was not enough evidence for anyone to be convicted. The verdict devastated Susan's mum Evelyn Winburn. "You would expect that the people that did this awful, awful thing to my daughter, that they would be brought to justice," she said.