Campaign groups have cast doubt on the conviction of Jill Dando's killer Barry George.

The obsessive loner and convicted sex attacker has begun a life sentence after he was found guilty by a majority verdict of killing the BBC TV presenter outside her west London home in April 1999.

He denied the shooting and his lawyers are preparing an appeal.

John McManus, from the Miscarriages of Justice campaign and support group, said the case had all the hallmarks of an injustice, but warned that George was unlikely to succeed.

If he killed her to become famous why hasn't he confessed? He doesn't fit the profile

John McManus, Miscarriages of Justice campaign

"It is a Catch 22 situation for him," he said.

"He has been convicted on circumstantial evidence but the Court of Appeal will not look at anything based on circumstantial evidence.

"He needs fresh evidence, but it's going to be very difficult to find."

If denied an appeal court hearing, supporters believe George's only option would be to apply to the Criminal Cases Review Commission, which could take several years to reach a decision.

George's legal team must decide on what grounds to appeal against his conviction.

'Fundamental mistakes'

This could be on disputed aspects of the prosecution case, such as the identification or forensic evidence presented.

Author Brian Cathcart, who has written a book about the murder, told the BBC that "fundamental mistakes" had been made in the murder investigation.

Miss Dando was found dead on her doorstep

He said: "That a coat which had been sealed in an evidence bag should have been removed from that bag to be photographed and then replaced in that bag.

"That it was photographed in a studio where firearms were also photographed. It beggars belief."

"There is the absence of the motive, the disputed forensic evidence," he said.

"You had a vulnerable defendant who the defence undoubtedly believed was incapable of speaking on his own behalf and withstanding cross-examination."

After the trial it emerged that George, who had a history of stalking women, had once served a prison sentence for attempted rape.

The evidence that convicted George

Gunfire residue on his coat A clothing fibre at the crime scene Eyewitnesses placed him at the scene He was fascinated with guns He was obsessed by celebrities and the BBC

He was also arrested outside Kensington Palace, the home of Diana, Princess of Wales, in 1983 dressed in combat gear and with a 15ft rope coiled around his chest and a commando knife strapped in his belt, but was not charged over the incident.

Police searching George's flat found more than 2,000 undeveloped photographs of 419 different women he had followed around London and secretly photographed.

They also found a stash of gun magazines and a photograph of George wearing a gas mask and posing with a pistol.

George will be assessed at Belmarsh Prison to determine what category prisoner he will be, and then moved to one of five prisons.

An independent inquiry into the murder has been set up by Ealing, Hammersmith and Hounslow Health Authority, with Hammersmith and Fulham Council and the Department of Health, and is expected to publish a report by the end of the year.