POLICE have found the missing kitchen knife that killed special constable Nisha Patel-Nasri, complete with DNA of the killer on it.

Mrs Patel-Nasri, 29, was alone, in her night dress and carrying a torch when she was stabbed to death outside her Wembley home just before midnight on May 11.

Officers also have CCTV footage of an Audi A4 acting in an "extremely unusual manner" twice on the night of the stabbing, Detective Superintendent Julian Worker said.

The car may have picked up the suspect, a black hooded man seen running away from the scene, in Harrowdene Road, which runs parallel to Sudbury Avenue, where the Patel-Nasri's lived.

"We're just missing the name, because the rest of it's there now," Mr Worker said.

It's still unclear if Mrs Patel-nasri had taken the knife with her to investigate a possible burglary, or if the suspect took the knife from the kitchen and chased the hairdresser out of her home.

The Saturday before the murder there was a disturbance outside their house, while the murder may also have been connected to Mrs Patel-Nasri's work as a Special Constable in Brent.

Mr Worker said police had eliminated one suspect from a previous incident in her voluntary work.

The other possibility is that it could have been linked to her husband's limousine business.

Fadi Patel-Nasri had recently sold a limousine and the suspect may have believed there was cash in the house.

Killer's DNA found

Mr Worker added that blood from Mrs Patel-Nasri found on the knife led police to believe it was the murder weapon.

Scientists also found enough DNA of the killer on the knife to create a profile that can confirm or eliminate a suspect in the case.

But it could not run the profile against the national DNA database, as was done in the murder of Croydon model Sally-Anne Bowman.

For "operational reasons" police would not say where or when the knife, a 30cm John Lewis Evolution cooking knife, was found.

Mr Worker said Mrs Patel-Nasri's husband was not a suspect and never had been. He confirmed that Mr Patel-Nasri was out on the night of the murder, but it was not on the anniversary of one of the couple's three wedding ceremonies.

Officers are looking for a light grey or silver coloured Audi A4, manufactured between 2001 and 2004.

On the night of the murder the left light on the back of the rear number plate was not working, while the skirts were black and did not match the rest of the car.

Officers also believe the car may have had a mark on the rear of the roof. Police are now eliminating 6000 Audi A4s in the country one by one.

CCTV cameras at a tile shop in East Lane filmed the car one hour before the murder as it drove up Harrowdene Road.

Police want to speak to a witness who ran towards the car at the junction with East Lane.

The car then turned around and drove back down Harrowdene Road.

Immediately after the murder it returned and stopped short of the junction for seven seconds and then impatiently moved forward before the traffic lights changed.

Potential witness

Police have also released CCTV footage of a man walking southbound on Harrowdene Road on the date of the murder.

The man may have seen the car and its occupants and police are anxious to trace him, as he may be a potential witness.

He is described as black, wearing white trainers, light green trousers and a burgundy coloured top and a dark coloured jacket. He was carrying a bag over his right shoulder.

There is a reward of £40,000 for information that will lead to the arrest and conviction of the killer.

Anyone with any information should call the incident room on 020 8247 7821, or call Crimestoppers anonymously on 0800 555 111.