At the start of Should I Marry a Murderer?, Dr Caroline Muirhead feels instantly relatable. She hangs out with her friends, has endured a painful heartbreak, posts Snapchats with embarrassing filters, and has been told by men that she’s “too much” — honestly, hard relate. By the end of the three-part Netflix documentary, however, we’re left with the portrait of a broken woman who made a decision no one could have imagined.
Should I Marry a Murderer? follows Muirhead through her relationship with Alexander “Sandy” McKellar, and how, shortly after their engagement, he revealed a dark secret from his past. The series is already being positioned to rival recent true-crime hits like Trust Me: The False Prophet and The Truth and Tragedy of Moriah Wilson.
Here’s everything we know about Dr Caroline Muirhead, her role in solving a missing persons case, and her life since the documentary aired.
Who is Dr Caroline Muirhead?
Caroline was a pathologist living and working in Glasgow. She had met many of her close friends during medical school and had previously been in a serious relationship during her studies. An only child, the documentary displays how close Caroline was to her parents.
After a difficult breakup, 29-year-old Caroline struggled to get back into dating, until she met Alexander “Sandy” McKellar.
How did Caroline and Sandy meet?
Caroline and Sandy matched on Tinder, and she immediately shared her phone number with him. Sandy invited her to the estate where he lived and worked, and Caroline impulsively agreed to go.
“I felt so lonely and wanted to find someone who didn’t want to change me and someone who would want to start life together with marriage and the prospect of children," Caroline explains in the documentary.
“You cast your net wide and see what happens. Then I saw this gamekeeper pop up."
“His profile hit me, and he was in a kilt and said he was a 6ft 4 lonely Highland contractor looking for someone to keep him warm on cold nights on the farm.
“He had a hunting agency, and I liked that sort of idea of a man who, if Armageddon came, could fix anything and hunt anything. A man’s man."
The pair soon found themselves hiking together and falling head over heels, swept up in a whirlwind romance that quickly escalated into an engagement, much to the shock of their friends and family.
How did Caroline find out about the crime?
After celebrating their engagement with friends, Caroline asked her fiancé if there was anything she needed to know. Sandy grew sombre, and she briefly worried he might have a secret family hidden away somewhere. Instead, he revealed something far darker: years earlier, he and his twin brother, Robert, had hit a cyclist while driving under the influence. Rather than calling for help, they switched vehicles and buried the body.
Caroline was suddenly one of the only people in the world to know the truth. Back home, she began searching missing persons cases and discovered that, around the same time three years ago, Tony Parsons had disappeared during a 104-mile (167km) charity bike ride from Fort William to his hometown.
The cold case solved by a Red Bull can.
Caroline was left with an impossible decision.
“Imagine you fell in love with someone who made you feel accepted, wanted, seen, whole and loved and just special," she explains in the documentary.
“Then they’d say to you they did a horrible, horrible thing, something so vile it flips your entire world upside down."
“To remain in love, you have to keep the secret even though you know it will destroy you. But if you reveal it, you destroy everything too."
What happened to Dr Caroline Muirhead?
When shown by Sandy where the body was buried — as he wanted her help moving it — Caroline left an empty Red Bull can at the site to mark the location.
She reported the crime on December 27, and the twins were arrested three days later. During police interviews in Glasgow, both men refused to comment. Acting on Caroline’s information, officers discovered the body at a so-called “kill site,” where hunters leave animal remains.
Despite this, Caroline remained romantically involved with Sandy, even allowing the brothers to stay at her apartment in Glasgow. She continued to gather evidence but felt deeply conflicted about leaving the relationship — a fact that was later used against her.
By the time the trial approached, Caroline had begun to spiral, drinking heavily and using illegal substances. She failed to attend her court summons to testify and instead went searching for the missing bicycle, seeing it as a way to share the burden of evidence. She was eventually apprehended by police and placed in a cell. Meanwhile, the prosecution and defence agreed on a plea deal: Sandy pleaded guilty to a lesser charge of culpable homicide and was sentenced to 12 years, while his brother received just over five.
Caroline has also spoken about the lack of support she received from the police, noting she was not referred to victim services during the process.
She said, “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. This has to change.
“It is vital that services take a trauma-informed approach to witnesses, ensuring staff are both trained to recognise trauma responses and are able to provide appropriate support.”
A cold case solved by a confession between fiancées.
Is Caroline dating someone new?
At the end of Should I Marry a Murderer?, Caroline reveals that she is now in a new relationship and feeling genuinely happy. She has returned to her work and is spending more time with her friends and family, rebuilding a sense of normality after everything she endured.
She was in contact with the family of Tony Parsons, and has spoken about seeing the documentary as an opportunity to shed light on her experiences and to help other victims who don't receive support. The documentary credits mentioned that she made multiple complaints against Police Scotland, and that after a five-year investigation, the majority were not upheld.
Tony's son Mike said that without Caroline's intervention, it was unlikely that his body would ever have been found – and expressed the family's gratitude for what she had done.
Should I Marry a Murderer? is on Netflix now.
