Rachel Nickell was killed on Wimbledon Common, London, with her small son and their dog on July 15, 1992. They looked to be sexually motivated since she had 49 stab wounds. The Metropolitan Police Department conducted the original inquiry, centred on a local guy called Colin Stagg but ultimately cleared him of any wrongdoing. After ten years, with modern DNA testing, a cold case inquiry was opened to find Rachel’s murderer.
The Failure of the Original Investigation
Adhesive tape samples were taken from Rachel’s body, hoping to find male DNA that didn’t match Rachel’s husband or their son. However, scientists at the Metropolitan Police Forensic Science Laboratory failed to find any DNA, and it seems they didn’t question why. The tape should have been covered in Rachel’s DNA and skin cells.
To persuade Stagg to admit to murdering Rachel, an undercover policewoman pretends to develop love feelings for him. Even though Stagg never admitted guilt, he was arrested in August 1993. One year later, the entrapment evidence was suppressed at his trial, and Stagg was found not guilty.
The Cold-Case Investigation
Forensic Alliance’s forensic experts joined the Operation Edzell cold case inquiry into Rachel’s death in 2002. The case was handed to Roy Green, who was helped by his team. Mike Gorn worked on the chemical side of things, while Clare Lowrie handled the fibres (both hair and fabric). Andy McDonald handled the DNA testing, while April Robson was the head forensic investigator.
The first phase of the investigation involved examining items of clothing retrieved from Rachel and her son, Alex. The second phase involved re-examining the body samples and tapings taken from Rachel’s body. The last scientific team used a DNA profiling test called Low Copy Number (LCN), but the new couple decided to start with a standard DNA (STR) profiling test, with LCN only used if appropriate.
When the team looked at the tapings extract from the previous tests, they found a mixed profile using the standard method. The significant component appeared from Rachel, while some minor features were from a male. The LCN technique was over-amplified, leading to an excess of DNA and no result.
The scientists returned to the original tapes and re-sample them to create their extracts because they were intrigued by the small amount of male DNA. The second round of testing yielded a comprehensive profile from Rachel but just a little result from male DNA. More was needed to identify who it might have originated from.
The team then took a different approach and used a newer, more sensitive DNA test called Touch DNA. This test allows the detection of minute amounts of DNA, even when it has been transferred from one surface to another. The team tested the tapings using Touch DNA and got a complete profile of the male DNA, which they could match to Robert Napper.
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