Most people keep a few things to themselves when they first start dating, but one man withheld a secret so severe it has since become the subject of a Netflix documentary.
Dr Caroline Muirhead and Alexander McKellar, known as Sandy, matched on Tinder in autumn 2020 and quickly hit it off.
The relationship moved at breakneck speed. Within weeks, McKellar proposed — but Caroline had no idea there was a shocking truth he hadn’t told her.
As they continued getting to know each other after the rapid engagement, Caroline asked her future husband if there was anything about him that she didn’t know — anything that could affect what lay ahead for them.
That’s when Sandy confessed that he had struck and killed charity cyclist Tony Parsons in Argyll and Bute, Scotland, in 2017. He also admitted that he and his twin brother Robert then buried Parsons’ body, which was not found for three years.
“He’s right beneath your feet when you shoot your clay pigeons,” Sandy told his fiancee when making the chilling confession.
Recalling the moment in the Netflix documentary Should I Marry a Murderer?, Caroline said: “It was something so vile, it flipped my entire world upside down.”
She was then faced with an agonising decision: protect the man she loved, or report what she had been told to the authorities.
“I knew I had to hand in the man I loved,” she said. But complications followed. After she made her report in December 2020, the twins were released on bail only days later — unaware that Caroline was the one who had gone to the police.
Despite everything, Caroline remained with Sandy while quietly assisting the investigation. At one point, she returned to the estate with him and discreetly dropped a can at the burial site, later alerting police to the exact location.
The brothers were arrested again in December 2021 and charged with murder, after previously attempting to plead guilty to causing death by dangerous driving.
Reflecting on the aftermath, director Josh Allot said: “She expected the brothers to be remanded in custody, face trial and be in prison forever and be out of her life but they were thrust back into her life.”
“She had her whole life on track and after meeting Sandy and hearing what he did, everything falls apart.”
Caroline was scheduled to give evidence, but she broke down and did not arrive on the first day of the trial.
Sandy was later sentenced to 12 years in prison, while Robert received five years and three months.
Caroline has since spoken about why she chose to share her experience, saying she wants it to help drive change — including better safeguards for victims and witnesses.
“I hope by speaking out and sharing what happened to me, we can start an honest conversation about greater protection for victims and witnesses and why a far deeper understanding of mental health within the police and court system is so desperately needed.
“All too often the impact of trauma and abuse is overlooked or dismissed entirely and this means people like me are being left high and dry to pick up the pieces alone.”
Caroline, who has since moved forward with a new partner, described Sandy as ‘a coward and a killer’.