The Witness true story: How was Rachel Nickell’s killer eventually caught?

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Please be advised that this article contains descriptions of very sensitive and potentially upsetting topics, including murder and sexual assault. Reader discretion is advised.

Netflix’s three-part documentary, The Witness, tells the story of the 1992 murder of Rachel Nickell and its devastating impact – not only on the country, but especially on her partner, André Hanscombe, and their son, Alex.

After witnessing his mother’s murder, Alex became a major focus of public and media attention. The constant intrusion of the press led his father, André, to decide they needed to move to another country to keep Alex safe.

This compelling true crime story not only reveals the complicated and often difficult relationship between a father and son following a tragic death, but also highlights serious errors made by the police during the investigation. As a result, an innocent man suffered, and the real killer remained free to commit another horrific crime, taking the lives of Samantha Bisset and her young daughter, Jazmine.

Released alongside the series The Witness is a documentary, The Murder of Rachel Nickell, which explores the details of the case. It investigates who killed Rachel Nickell, and later, Samantha and Jazmine. Learn the true story behind the Netflix series by reading on.

The Witness true story: How was Rachel Nickell’s killer eventually caught?

On July 15, 1992, Rachel Nickell was killed on Wimbledon Common in broad daylight. Her two-year-old son, Alex, was the only person to witness the attack.

Although Alex wasn’t physically hurt, he was able to describe the attacker, making him a crucial part of the police investigation into Rachel Nickell’s murder. The book, The Murder of Rachel Nickell, reveals that Alex was hesitant to discuss the event and was visibly traumatized by witnessing the attack. He underwent multiple interviews as investigators sought details about the assailant.

Alex finally recalled that the attacker was a young white man dressed in a white shirt and blue trousers, with brown shoes. As André details in the documentary, a crucial detail was the killer wearing a belt over his shirt, which looked similar to a butcher’s apron. This description matched a sighting reported by a local woman, who claimed to have seen the same man carrying a bag near the crime scene about ten minutes before the murder took place.

So, the police had a suspect in this case, but they were hitting dead ends trying to locate him. That’s when they brought in a criminal psychologist, Paul Britton, to help build a profile. Eventually, they put out a description of the killer on Crimewatch, hoping someone would recognize him. And wouldn’t you know it, after the show aired, the hotline lit up! A few people called in saying the artist’s impression looked just like a guy named Colin Stagg.

Investigators noted that Stagg appeared to match the psychological characteristics of the killer, and he had previously stated he was in the area when Nickell’s body was found. Furthermore, the woman who saw someone near the Common shortly before the murder later identified Stagg in a police lineup.

When police searched Stagg’s home, they found zodiac signs painted on the floor and survival gear. This led them to believe he wasn’t an ordinary person, but without any physical evidence linking him to the crime, they couldn’t arrest him for Nickell’s murder and had to let him go.

Police received a tip from a woman who had been corresponding with Stagg through a pen pal club and found his letters unsettling, ultimately sharing them with authorities. This led to a controversial undercover operation where a female officer attempted to elicit disturbing sexual writings from Stagg. He responded to her, and thirteen months after the murder of Nickell, police arrested him as a suspect.

As a true crime and film buff, I remember when the news broke about Samantha Bisset and her young daughter, Jazmine, being murdered in their London home in November 1993 – just sixteen months after the Nickell case. It really sent shockwaves through the city. The police, understandably, brought in David Britton again to consult. The idea that the Bisset and Nickell killings could be linked came up, but the team originally focused on Michael Stagg – they were so convinced he was the guy, and believed he’d be behind bars by the time the Bissets were killed, so they dismissed the connection.

Detective Superintendent Mickey Banks requested a re-examination of the fingerprints found at the Bisset crime scene after initial tests showed no matches. When Samantha’s prints were tested again, investigators discovered several other fingerprints belonging to a man named Robert Napper.

So, this guy, Napper, was a local from Plumstead, and it turned out he’d been arrested before – that’s why they had his fingerprints on record. He eventually became the prime suspect in the Bisset murders, and during questioning, it became pretty clear he wasn’t all there, often referring to himself as ‘he’ instead of ‘I’. When the police searched his room, it was seriously creepy. They found a toolbox full of knives, a book about strangulation – seriously unsettling – and a London street map covered in drawings. He’d even circled an area near Wimbledon Common, which definitely raised some red flags. It all painted a really disturbing picture.

Stagg was put on trial for Nickell’s murder, but the case was dismissed by the judge. The judge ruled that the police’s use of a ‘honeytrap’ operation constituted entrapment and couldn’t be used as evidence.

After ten years, the investigation into the Nickell case had stalled, and police turned to forensic scientist Dr. Angela Gallop for assistance in finding the attacker. She and her team spent two years developing a novel method to analyze the DNA found alongside Nickell’s in the evidence. Ultimately, this analysis revealed the DNA didn’t belong to Stagg.

I was stunned when the DNA results came back – there was a match, and it led me right to Napper. He was actually in Broadmoor Hospital at the time, serving a sentence for the horrific murders of Samantha and Jazmine Bisset. It was an unbelievable connection.

What were Robert Napper’s other crimes?

After André returned to the UK for Napper’s trial in December 2008, a police officer shared a file with him proving that the murder of Nickell could have been stopped.

The documentary revealed that three years before Rachel, Samantha, and Jazmine were murdered, a serial rapist was targeting women – sometimes those with their children – along the Green Chain Walk in Southeast London. Police had a DNA profile of a suspect and, after releasing an artist’s impression, two women came forward to identify Napper as the possible attacker.

Detectives asked Napper to provide a blood sample, and he agreed, but he never came to the police station. When officers went back to his home, they discovered he had left and packed his belongings. Because he was taller than the descriptions given by the women he assaulted on the Green Chain Walk, investigators decided he wasn’t a likely suspect. This allowed him to continue committing crimes, and tragically, he later killed Rachel, Samantha, and Jazmine.

However, that wasn’t the only mistake the police made. According to André, in September or October of 1989, Napper’s mother told the police her son had admitted to raping a woman in Plumstead Common. Despite this information, the police never investigated the claim.

Where is Robert Napper now?

In 2008, Napper confessed to and pleaded guilty to the murder of Nickell, leading to his conviction.

He received diagnoses of both schizophrenia and Asperger syndrome. He was later found guilty of manslaughter, but due to his mental health, his responsibility for the crime was considered reduced. As a result, he was sentenced to be held at Broadmoor, a high-security hospital, for an indefinite period.

“You are on any view a very dangerous man,” Mr Justice Griffiths Williams said.

The judge continued, stating that the defendant stabbed the victim 49 times, continuing to stab her even after she had died. He noted that Alex was present during the attack, and the injuries on Alex’s face indicated the defendant likely dragged him away from his mother at some point.

After sixteen years, now as a young adult, Alex has learned that the man who murdered his mother has finally been brought to justice. This might allow him to finally move past this difficult part of his life and begin to heal.

What actions did André and Alex take against the Metropolitan Police?

I was absolutely floored by the ending of The Witness. Learning about that dossier… it just hit me so hard. André is completely justified in his anger, realizing Rachel, Samantha, and Jazmine might still be here if the police had taken Napper seriously from the beginning. It’s a devastating thought, and it really puts everything into perspective.

After obtaining a leaked document, a father and son officially complained about the Metropolitan Police, resulting in a highly critical report from the Independent Police Complaints Commission.

According to Rachel Cerfontyne, who was an IPCC Commissioner at the time, the investigations into the Green Chain rapes and the murder of Rachel Nickell were marred by a series of poor choices and mistakes made by the Metropolitan Police.

Police didn’t properly investigate when Napper’s mother reported he’d confessed to raping a woman. Surprisingly, they then ruled him out as a suspect in the Green Chain rapes simply because he was over six feet tall.

If not for these mistakes, Robert Napper might have been stopped before he tragically killed Rachel Nickell and the Bissets, and before he assaulted so many other women.

Cerfontyne admitted the police force had made “terrible” errors, but explained that no officers were formally disciplined. With the exception of one senior detective who had passed away, all the officers involved had already retired.

The end of the game The Witness shares a heartwarming message: André and Alex, a couple living in Spain, are still together and strongly believe in the importance of faith, hope, and love – and their bond is stronger than ever.

For information and support, please visit The Survivors Trust or Rape Crisis.

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The Witness and The Murder of Rachel Nickell are available to stream on Netflix.

Authors

Morgan CormackDrama Writer

Morgan Cormack writes about TV and streaming drama for TopMob. Before that, she was an Entertainment Writer at Stylist. She also has experience in content marketing, freelancing, and holds a degree in English Literature.

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2026-06-04 11:37