The murder case of Robert Higgins, who was brutally killed in 1995, has been re-examined by experts in a new BBC Scotland series.
His body was found dumped in an unused quarry in Kirkliston, near Edinburgh, a couple of days after he failed to return home from a night out at the pub.
His killer still remains a mystery - and the cold case is the topic of an episode of David Wilson's Crime Files: Cold Cases which airs tonight at 10pm on BBC Scotland.
In the episode, the Scottish criminologist speaks to forensic scientist Dr Helen Meadows about his injuries and potential murder weapon.
And crime reporter Jane Hamilton, who previously worked for the Daily Record and covered the case when it happened, discussed how "one murder in a small town, with several suspicious aspects to it, still leaves questions to this day".
Despite being relatively well known where Robert lived in Dalmeny, as well as Kirkliston and South Queensferry, nobody could explain where he was or who he was within the three days leading up to his death on May 1, 1995.
And nearly 30 years later, his death remains a mystery - even in the tight-knit community he was a part of.
Who was Robert Higgins?
Known as "Higgy" amongst his friends, Robert Higgins was a hardworking poultry farm worker who lived with his elderly mother in the village of Dalmeny.
He was described as a "creature of habit" - every week he would go out to work Monday to Thursday, then spend his weekends drinking in the pubs around Kirkliston and South Queensferry with his friends.
But no matter where he went, he always returned home to his mother's house - until Thursday, April 7, 1995, when he left his set-in-stone routine behind and never came home from Kirkliston.
Talking about the case, David Wilson said: "Starting off with pals at the Kirklands pub, he left just after midnight - but was still on Kirkliston's main street at 2 o'clock in the morning. A pal he often stayed at was busy that night, he couldn't book a taxi, and so he didn't make it home.
"Unusually for Robert, he didn't phone his mother to tell her he was staying out."
Across the weekend, he was spotted a couple more times drinking in bars around South Queensferry - but witnesses say he was with a "middle aged couple" that nobody recognised or has ever come forward about.
And despite people claiming he looked "clean-shaven, tidy and relaxed", his battered body was found at Lindsay's Craigs quarry on Monday, May 1.
How did Robert Higgins die?
Robert's final days are a mystery. The police released images of the couple he was believed to have been spotted with, but they have never been identified.
Police also ruled out burglary as a motive, and his body didn't display any defensive wounds.
Speaking on the BBC programme, resident forensic scientist Dr Helen Meadows confirmed that his cause of death was sharp-force trauma, or stabbing in the left side of his ribcage.
A kitchen knife was found near to the scene of the crime where Robert was killed, and has become "part of the narrative" of the story, which David described as "astonishing".
He said: "The murder weapon [was] believed to be a common kitchen knife. It had been taken from the crime scene and apparently found by a woman who took it home to chop vegetables with, thus washing it clean of any potential forensic evidence."
But would this have destroyed every piece of evidence found on the knife?
Dr Helen said: "Even if it was just rinsed with water, you'd remove all water-soluble evidence from the knife such as DNA. In terms of fingerprints and blood, there's still an insoluble element to evidence, which could persist if it was just water alone."
But due to the nature of the crime, it's likely the knife was washed repeatedly with bleach or detergent, which would have removed the evidence.
The exact weapon, along with the killer, still remains a mystery.
Will the case ever be solved?
Only one man has ever been tried for Robert's murder. It was in 2007, and he was thought to be the suspect because of DNA found on his leather jacket.
But he was acquitted by the 'not proven' verdict, as the jury "could not make up their mind", according to crime reporter Jane Hamilton.
She described him as a "gentle creature of habit" but his manner apparently changed in the week before his disappearance.
"He wasn't a secretive person, but he was very shy. His mum and sisters noticed a change in him. He'd been in the pub the previous weekend and told a friend that he was going to bring his girlfriend in the next week," she explained.
"This was a surprise to everybody, he hadn't had a girlfriend in a number of years. He wasn't an unhappy man, but he seemed a lot more jollier and happier."
Despite this, no girlfriend ever came forward when he was found dead.
But Jane thinks the murder case may still be solved eventually, thanks to DNA.
"If not, maybe someone having the conscience to come forward and say 'I was there, I know what happened to Robert.'"
David Wilson's Crime Files: Cold Cases airs on BBC Scotland on Tuesday October 18 at 10pm.
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