Dr Caroline Muirhead and Alexander ‘Sandy’ McKellar had a whirlwind romance.
Netflix’s latest true-crime documentary, Should I Marry a Murderer?, explores the shocking real-life case of a Scottish woman whose engagement led to the exposure of a hidden killing.
The documentary centres on Dr Caroline Muirhead, a medical professional who began a relationship in 2020 with Alexander McKellar, known as Sandy, after meeting him on Tinder. Their romance quickly progressed into an engagement, but the relationship took a dark turn when McKellar confessed that he had fatally struck a cyclist years earlier and concealed the crime.
The victim, Tony Parsons, was killed in 2017 in Argyll and Bute, Scotland, after being hit by a vehicle driven by McKellar, who was under the influence of alcohol. According to investigators, McKellar and his twin brother Robert later buried Parsons’ body on a remote estate, where it remained undiscovered for three years.
The three-part series is told largely through Muirhead’s perspective.
After learning the truth, Muirhead reported the confession to police. However, rather than ending the relationship immediately, she secretly cooperated with investigators while maintaining contact with McKellar.
Her actions proved critical to the case. She reportedly recorded private conversations in which McKellar discussed the incident and later revisited the burial site with him, discreetly marking the location so police could recover the body.
The brothers were arrested in December 2020, but formal charges were not filed until a year later, leaving Muirhead exposed to continued contact during the lengthy legal process.
Director Josh Allott said the emotional conflict at the heart of the story made it compelling, describing it as a scenario that forces viewers to question what they would do in similar circumstances.
The documentary also examines Muirhead’s criticism of how authorities handled her as a witness. She said she expected support and protection after coming forward but instead felt abandoned during a traumatic period.
Police Scotland declined to participate in the series. Following a five-year review of complaints made by Muirhead, most were not upheld, with the force maintaining that appropriate support had been provided.
In July 2023, shortly before trial proceedings in Glasgow, Alexander McKellar pleaded guilty to the reduced charge of culpable homicide. His brother Robert admitted attempting to defeat the ends of justice after his not guilty plea to murder was accepted.
Alexander McKellar was sentenced to 12 years in prison, while Robert McKellar received five years and three months.
The documentary presents not only a murder investigation, but also the psychological toll placed on those caught on the edge of serious crime.
