When pathologist Caroline Muirhead said yes to her boyfriend’s proposal after just a few months of dating, she couldn’t believe her luck. Her elation soon turned to horror when the man in question, Alexander “Sandy” McKellar, shared a secret he’d kept for years – that he had killed a cyclist and buried him with the help of his twin brother.
In 2023, Scottish brothers Alexander and Robert McKellar were convicted in relation to the death of Tony Parsons, who had disappeared while cycling between Scotland’s Bridge of Orchy and Tyndrum six years earlier. Alexander McKellar pled guilty to culpable homicide and attempting to pervert the course of justice after hitting Parsons with his car, leaving him to die and eventually burying him under the hunting estate that he worked on.
However, for a long time, he wasn’t aware that it was his fiancée, Muirhead, who played a major role in his arrest. The pathologist alerted police to the location of Parsons’ body by leaving a Red Bull can at the site during a visit with McKellar – risking her life to do so as McKellar, who had been on the grounds hunting, was carrying a gun at the time.
Muirhead’s side of the story immediately gripped filmmaker Josh Allcott, who directs Netflix’sShould I Marry A Murderer?– a new three-part documentary about her ordeal.
“When I first heard the story, I couldn’t believe that this was the real-life experience of a living person and not the plot of a drama,” he tells me. “It seemed just kind of unimaginable.
“I was fascinated about hearing more and the experiences of Caroline doing the right thing and going to the police, how that turned her life completely upside down despite her doing the right thing.
“I felt it raised quite interesting further questions about witnesses in the justice system and our treatment of them – there was a lot that hooked me in instantly.”
While an emotionally torn Muirhead went to the police a few weeks after McKellar’s confession, it took the authorities another year to charge the twins. During that time, she began her own form of investigation – secretly recording her conversations with McKellar while avoiding raising the suspicions of her husband-to-be.
“She thought that justice would be secured relatively quickly and [the Red Bull can] would be enough for the police to remand them in custody and for her to be able to move on with her life,” Allcott says. “That clearly isn’t the case.”
After finding Muirhead’s can, police dug up Parsons’ body and took it for a post-mortem at the primary hub for autopsies in that area – which happened to be Muirhead’s place of work of 11 years. As a result, she was placed on special leave from her job.
While Muirhead had tapered off contact with McKellar by this point, being out of work left her “devastated”. Feeling “abandoned” by the police, she subsequently rekindled her romance with McKellar, moved onto his estate and began using cocaine.
“That sucked her back into contact with Sandy and the feelings she’d had before she went to the police,” Allcott says. “It’s a toxic love story, and that idea that you can just turn off feelings for someone even if they have done something terrible is obviously quite black-and-white thinking.”
“My brain couldn’t fathom and cope with the idea that the man that I’d fallen in love with was a murderer,” she says in the show. “We had a bond, which obviously is not healthy at all, but it was a bond, and there was an awful lot of love.”
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Allcott anticipates that viewers will be surprised by some of Muirhead’s choices throughout the docuseries – but hopes that they go in with some understanding.
It’s a terrible, toxic love story that she found herself in and she’s not proud of it
Director Josh Allcott
“It’s impossible to imagine how any of us would react in this situation,” he says. “I was surprised when she decided to maintain a relationship with Sandy, having gone to the police and gathered evidence for them.
“But if you think about the circumstances that she was under, it turned her life upside down entirely. She wasn’t able to work, it was during Covid, she was incredibly isolated, she got involved in drugs and alcohol. He was the one thing she thought she could rely on to be something good for her in that situation.”
He added: “She’s been so incredibly brave to tell that part of the story and she’s done so for other people not to make the same mistakes she has. It’s a terrible, toxic love story that she found herself in and she’s not proud of it.”
The brothers were ultimately arrested – Alexander on suspicion of murder and Robert on the charge of trying to defeat the ends of justice. Muirhead, who was not deemed to be a vulnerable witness by the Head of Homicide and Major Crime and so was not provided with emotional and mental support, had been threatened with arrest if she did not testify against the brothers. On the day of the trial, she panicked and didn’t show up to court, leading to her own arrest.
As a result, the prosecution abandoned Alexander McKellar’s murder charge and asked to amend it to the lesser charge of culpable homicide. He accepted a plea and Muirhead was released from custody without a criminal record.
Alexander McKellar was sentenced to 12 years imprisonment, while Robert was sentenced to five years and three months of jail time after pleading guilty to trying to defeat the ends of justice. They both remain in prison in Scotland.
Former Navy officer Parsons, 63, had been on a charity bike ride from Fort William to his home town of Tillicoultry when he was hit by McKellar’s car. The grandfather was raising money for a prostate cancer charity, having successfully been treated for the illness himself.
“I loved him in uniform. I would see him in uniform and just light up,” his wife Margaret told BBC documentaryMurder Caselast year. “I was very proud of Tony. Very proud of what he did.”
While Allcott was unable to speak to the Parsons family for the documentary, he felt that Muirhead’s story was still worth telling.
“There was a bigger point to make with this story. It didn’t really feel like we’re just looking at a crime for the sake of it,” he says.
“There were questions raised about how we treat witnesses in the criminal justice system and how Caroline in the end didn’t participate in the trial. Perhaps if she had been treated differently through that process, they would have been able to secure a different level of justice for Tony Parsons’ family.”
Should I Marry a Murderer?is now streaming on Netflix.
