The elusive killer

Police do not have a firm motive for Jill Dando's murder

By the BBC's Jeremy Britton

The sweating man by the bus stop, the man in the Range Rover, the man dressed like an estate agent - there are many clues to the identity of Jill Dando's murderer.

But despite unprecedented publicity and hundreds of calls resulting from Crimewatch appeals, the white, middle-aged murderer the Met police have searched for around the world remains frustratingly elusive.

In many ways it should not be a difficult case to crack. A TV celebrity is shot in broad daylight in the middle of a busy west London street by a man seen hanging around by a dozen witnesses up to two days beforehand.

Within a week the police have produced an artist's impression of the prime suspect.

The police e-fit of the suspect

The senior investigating officer, Detective Chief Inspector Hamish Campbell, also has valuable forensic clues to base his inquiry on such as the bullet itself - which unusually had been tampered with, possibly to reduce the noise of the shot.

The evidence points to someone with a good knowledge in firearms who has used a gun with a hollowed-out barrel to carry out a carefully planned assassination.

Yet the lack of a clear motive for the murder quickly creates a number of different theories.

Previous boyfriends

The apparently professional nature of the killing initially leads to speculation that the murderer had connections with Serbia - then involved with the war in Kosovo.

Officers also question top criminals around the UK who might have been convicted as a result of a Crimewatch appeal and feel angry enough to employ a hitman in revenge.

At the same time Jill Dando's love life comes under close scrutiny from the press - have any of her past boyfriends become jealous of her forthcoming marriage to hospital consultant Alan Farthing?

Jill had several relationships before settling down with Mr Farthing. But the police are quick to rule out any of her past boyfriends as suspects.

Stalker theory

The possibility that Jill has fallen victim to a celebrity "stalker" also has to be considered seriously.

It is well known that various internet sites show an unhealthy interest in Jill Dando and like many other TV personalities she has been written to and even visited by members of the public obsessed with her glamorous image.

Forensic psychiatrists employed by the police also produce a profile of the suspect as an obsessional loner.

Hundreds of people rang police with information

But if the murderer was a misfit, somehow fixated to Jill Dando, who spent time tracking her down and watching her house - how does this square with the image of a detached, professional gunman?

In their latest Crimewatch appeal last week, police asked the public for help in tracing exactly this sort of person and were surprised by the number of names put forward.

Detectives are now working through all the new leads.

Yet one year on there has still been no major breakthrough.

Senior detectives with experience of long-term investigations say that keeping up the morale of the investigating team becomes ever more important.

The next phone call, the next witness statement could be the one that turns the investigation from a fruitless trawl into a success against all the odds.