Sarah's murder has become a ratings winner

It is four months since the body of Sarah Payne, the little girl whose abduction prompted a frantic nationwide search during the summer, was discovered in a field near Pulborough in Sussex. At the time, several factors combined to ensure that the murder received an extraordinary amount of attention: her family's desperate belief that she was still alive, their willingness to talk to the media, and the fact that child abduction has a peculiarly horrible resonance in this country after the murder of the Liverpool toddler, James Bulger, in 1993. Last week, Sarah's trusting face appeared on television and in newspapers again for the first time in weeks, a shocking reminder of how much time has passed since the investigation began.

It is four months since the body of Sarah Payne, the little girl whose abduction prompted a frantic nationwide search during the summer, was discovered in a field near Pulborough in Sussex. At the time, several factors combined to ensure that the murder received an extraordinary amount of attention: her family's desperate belief that she was still alive, their willingness to talk to the media, and the fact that child abduction has a peculiarly horrible resonance in this country after the murder of the Liverpool toddler, James Bulger, in 1993. Last week, Sarah's trusting face appeared on television and in newspapers again for the first time in weeks, a shocking reminder of how much time has passed since the investigation began.

It happened not because of developments in the case, but in a context that raises uncomfortable questions about the relationships between the police, the media and the families of murder victims. On Wednesday evening, Sarah's grandfather narrated a reconstruction of the abduction for the BBC's Crimewatch programme, while ITV's Tonight with Trevor McDonald showed a feature on her parents. There is no doubt that it was compelling viewing: unofficial overnight figures suggested that the feature boosted the audience from an average of 5.5 million for earlier programmes in the series to 6.6 million, or 34 per cent of viewers.

After the Crimewatch programme, which prompted 350 phone calls, detectives said they were investigating several leads, including information about a lorry driver involved in a near-accident at Pulborough on the day of the murder. They were also hoping to interview a woman who had apparently spotted the girl's missing dress, not far from where the body was discovered. No one explained why, if she possessed this vital piece of information, the woman had not come forward earlier. Back in mid-July, the police had already received almost 30,000 calls from the public, indicating an unusual willingness to help, if not hard information. You would have had to be abroad, or in a coma, to miss the grim drama as it unfolded, with endless graphics explaining the child's last known movements and sightings of suspicious vehicles.

By Friday morning, the optimism generated by the Crimewatch programme was draining away as the police admitted they had suffered what one tabloid described as a "crushing setback": when they traced the lorry driver, it turned out that the incident in question had been on a different date. None of this is surprising, although it must be incredibly painful for the family to have their hopes raised and dashed once again. Equally worrying is the way in which, as long as the media maintains its obsession with the case, the public is encouraged to imagine the killer as a kind of bogeyman, with almost supernatural powers to evade capture and menace other people's children. Yet it is well-known that stranger-murder, of which this is almost certainly an example, is one of the most difficult crimes to solve.

Add to this the fact that the trail had gone cold by the time Sarah's body was found, 17 days after her disappearance, and it becomes obvious that a swift resolution was never likely. The tactics adopted by the police at the time suggested as much, relying on emotional appeals from Mr and Mrs Payne and Sarah's siblings which were almost unbearable to watch. My guess is that the inquiry stands today pretty much where it has always been: no DNA samples, no prime suspects, and not much more evidence than became available with the discovery of the body.

In that sense, the police have almost certainly created an appetite for developments in a case where they will come painfully slowly, if at all. What, then, is achieved by going over the details again? Haven't we passed the point where public interest tips over into prurience? The Tonight programme took a different tack, sending a reporter to the US with Mr and Mrs Payne to see how Megan's Law, which allows access to a register of paedophiles, is working - an inquiry which could have been carried out just as effectively, and less emotively, without their presence.

The fact that the Payne family have chosen to co-operate with journalists does not prove they are not being exploited; desperation clouds judgement. But it is surely clear by now that reconstructions and appeals to the public have reached the limit of their usefulness in this case. There is a moment when tragedy becomes spectacle, when members of the public cease to be potential witnesses and become instead voyeurs. That line, I think, has already been crossed in this extremely distressing case.