Police to 'grow' DNA from samples to trap mother's attacker

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Forensic science experts are using innovative DNA testing techniques to help police bring to justice the knifeman who stabbed Abigail Witchalls, paralysing her.

Forensic science experts are using innovative DNA testing techniques to help police bring to justice the knifeman who stabbed Abigail Witchalls, paralysing her.

Home Office scientists have been drafted in to analyse evidence obtained by the 100-strong major crime team for traces of DNA. They will then "grow" under laboratory conditions anything they find on these swabs, including fragments of skin cells or minute traces of saliva. This is in an attempt to produce a large enough sample or genetic fingerprint which can then be matched against a potential suspect.

The painstaking process may take up to a month but could provide the break-through police need, helping them to use evidence which the offender had left behind at the crime scene.

The forensic scientists have already taken swabs from the pushchair which Mrs Witchalls was pushing when she and her 21-month-old son, Joseph, were confronted by a man in a secluded lane in Little Bookham, Surrey, nearly two weeks ago.

The part-time teacher was left for dead after trying to escape from her attacker who got out a car and chased her then held a knife to Joseph's throat before pushing her to the ground and stabbing her in the neck.

Police are working through the names of more than 30 possible suspects with a view to eliminating them from the inquiry or bringing them in for questioning about the attack, at 4pm on 20 April.

On Friday, they released a 25-year-old man after Mrs Witchalls failed to pick him out during a video identity parade. Terry Barnes, from Surrey, has now been remanded in custody in connection with an unrelated burglary charge. Police said they have not eliminated Mr Barnes from their inquiry and have carried out a forensic search of his home.

Mr Barnes is the third suspect to be arrested in connection with the knife attack. A man and a woman, both in their late twenties, were questioned on suspicion of the attempted murder. Detectives eliminated the woman from their inquiries and released the man on police bail.

The knife that Mrs Witchalls's attacker used has not been recovered despite an extensive search. Police are also looking for the attacker's car, originally described as a dark blue estate. Officers now believe this may not be correct and are using colour cards to get a closer description.

"This crime has touched the nation," said Detective Superintendent Adrian Harper, who is leading the investigation. "For the first time in my 22 years in the police I can't help but to take this case home with me. The dogged determination to catch this person cannot be underestimated."

The only witnesses to the stabbing are Mrs Witchalls and her son, who is too young to be interviewed. A planned reconstruction will start at the parent and toddler group they attended on the morning of the attack. Police also hope to create a computer image of the suspect with the help of Mrs Witchalls, who is communicating using blinks and facial expressions from her bed at St George's Hospital, Tooting, south London.

The young mother has given police a detailed description of her attacker. He is said to be between 20 and 35, about 6ft tall with scruffy dark hair, a long pale thin face, prominent cheekbones and bags under his eyes. He was wearing silver hoop earrings and had a deep voice with a southern or possibly cockney accent.