The police team, led by Detective Superintendent Stuart Cundy, launches a murder investigation. It is one of the largest ever undertaken by the Metropolitan Police Service. As they make their enquiries, one person starts to stand out as the potential killer. It’s Lewis Sproston, Sally Anne’s boyfriend and the last person to see her alive. He’s arrested on the Sunday afternoon. When questioned, he appears to confirm his guilt when he utters “is this about last night?” The police believe they have got their man. Crucially DNA from the killer is recovered from Sally Anne’s body. All they need to do is match the sample to Lewis. Swab tests are taken and processed, but there is no match and Sally Anne's innocent boyfriend is released.
It emerges that the killer may have been responsible for an earlier attack on Sanderstead Road, just 40 yards from the murder scene. At around 3.30am a woman pulls over to use her phone. Having no signal she gets out of her car. As a man approaches, she sees a knife and holds out her handbag as she believes she’s being robbed. After saying ‘sorry’, her attacker beats her over the head with a blunt instrument. She’s only saved when a passing taxi scares him off. After she’s given first aid, she realises that she’s been bitten. She provides the police with their first e-fit of the killer, but it provides no leads in solving the case. Progress is eventually made when the police cross-reference the killer’s DNA sample and find it matches another crime committed in 2001. In that case, a young woman from Purley was making a call from a telephone box when a man exposed himself to her. He then performed an indecent act and disturbingly tried to get inside the telephone box. The perpetrator was never caught. However the victim got a good look at his face. So four years on, and six months after the murder, the police release his e-fit to the media explaining the two cases are linked. They believe a further six sex attacks in the area may also be linked to Sally Anne’s murder. But despite three Crimewatch appeals, two e-fits, a £40,000 reward and the killer’s DNA and fingerprint, the police still don’t have any answers. They resort to drastic measures when on 27 February 2006 they urge 4,000 men in the local area to take part in a DNA screening procedure which will help eliminate them from their enquiries. Unbeknown to the police, the murderer is back in Croydon and one of his friends asks whether he’ll be taking part in the DNA screening. Without warning, he gets very aggressive, asking whether his friend thinks he’s the murderer. During the next couple of days he moves abroad to Amsterdam. The DNA screening fails to find the killer and the police are fast running out of options to help solve the case.
The breakthrough comes on 15 June 2006. England is playing Trinidad and Tobago in the FIFA World Cup and win the match. Mark Dixie, 35, is watching the game at his local pub with friends when an innocent man spills his pint over him. Erupting into a violent outburst, he gets the man outside, where in full view of two Police Support Officers, he pushes him. This fatal error sees him arrested and taken to Crawley police station. Here he is duly processed and a DNA swab taken. This will be all the police need. Two weeks later he will be arrested for murder.
Luckily for the police Dixie gives them his correct address. He’s been living and working as a chef at Ye Olde Six Bells pub in Horley, Surrey. His job could make his arrest problematic, so the police decide to create a story to get him out of the kitchen. They needn’t bother. As the two officers turn around they notice Dixie taking a cigarette break, and they take their opportunity to arrest him. He’s calm and unfazed by the whole incident. Disturbingly one of the officers notes how Dixie’s heart rate fails to change, which he finds chilling. Taken in for questioning and still appearing cold and emotionless Dixie answers ‘no comment’ to every question asked.
On closer inspection of his room, police make a sickening discovery. They find he has been masturbating to photos and video footage of Sally Anne Bowman, reliving her brutal and callous murder.