Of all the formal observances, a Police Press Conference is the most intriguing

Our ritual life may not be quite as rich as it used to be in some areas - agriculture, say, or childbirth - but there are alternatives for the anthropologist seeking employment close to home. Probably the most intriguing area of study would be modern ceremonies of information - The Manifesto Launch, The Film Premiere, The Doorstep Photocall by Philandering MP. On this last point, incidentally, Piers Merchant doesn't quite seem to understand the protocol: a supportive hug, yes, even a chaste and loving kiss, but definitely not the tongue-sandwich he visited upon his unfortunate wife. You half expected him to invite the assembled journalists into the bedroom, where he could conclusively demonstrate the satisfying vigour of his marital relations.

Of all these formal observances, though, each governed by its rules of performance and ritual utterance, the most interesting is the Police Press Conference. The latest example on our screens was not entirely typical. The wretched sight of a young scoutmaster recounting his feelings about his friends' capricious death beneath a rockfall certainly met the requirements for a display of numbed distress. It also provided a good example of the ceremonial placement on these occasions - the processional approach to a miked-up table, the flanking attendants (in this case also in scout's uniform), the police acolytes keeping a watchful eye on proceedings in case the congregation became unruly. But the purifying motive that is usually present - that of furthering the inquiry - was absent here.

It's true, of course, that not many people will be lighting fires in caves for the next few months, so it might be argued that public safety had been improved by the event. But that purpose was a little too slender to disguise the unmistakable odour of sacrifice that hangs over these affairs - the sense that a survivor is being offered up to appease the appetites of the media (and, by extension, us). Maybe such interrogations are therapeutic - some conferees have said as much - and maybe they are prophylactic, preventing the messy infestation of your life by a swarm of reporters; but neither of those justifications will stretch as far as us, the audience.

The scout leader conference also lacked another important element of the true Police Press Conference, one that has insinuated itself into the ritual and is - by powerful taboo - never spoken of during it. That is the question of guilt. In this case it was brute stone that was culpable but, more often than not, these have become occasions in which the innocence of the participants can never be taken for granted, even when they appeal most movingly for assistance in solving the mystery.

In a striking number of cases those whose grief has been deployed to stimulate public sympathy turn out to have committed the crime themselves. It would actually be surprising if this was not the case; close relatives and friends are the people most likely to be asked to take the leading role in such performances and, statistically speaking, the person you are most likely to be murdered by is a close relative or someone you know. Almost by definition, then, the chief suspect and the next of kin are bound to overlap from time to time. Film of convicted murderers expressing their fervent hopes for their own discovery has become commonplace.

In the two most recent cases of child murder the person finally charged with the crime first appeared on police press conferences about the case, their faces fixed in a mask of distress and disbelief. That last sentence, incidentally, is not meant to convey any presumption of guilt, because it is one of the peculiarities of these occasions that they require everyone to act a part, the innocent and the guilty alike. Even the presiding police officers must compose their features into an appropriate look - a blend of sympathy and vigilant determination.

But we have so often had to revise our first impressions, so often tried to tell ourselves that all along we knew there was something dubious about the bereaved husband or something suspect in the body-language of the boyfriend, that now, faced with one of these formal expressions of distress, we are as likely to interrogate it for authenticity, as to respond to it with any generous empathy. When the parents of the two children swept off a Norfolk beach first appeared on television to describe their feelings and solicit information I can't have been alone in wondering - quite erroneously of course - whether they knew more than they were saying - in fact I know I wasn't because I've asked other people, shocked by the wary cynicism of my instincts.

And the false notion that there is a right and wrong way to behave in such circumstances (for which we casually substitute "genuine" and "false") can be dangerous. When Cheryl Tooze campaigned for the release of her fiance Jonathan Jones, after he had been convicted of murdering her parents, some of her family turned against her, citing as one provocation for their bitter opposition that her performance at the police press conference had been unconvincing, they felt, that she did not come across as sufficiently distraught.

Presumably, though, it would be regarded as slightly suspicious to refuse to take part in such a ritual, as if you feared that brilliant light. In its implicit faith in the revelatory nature of the ordeal the Police Press Conference has become more like a witch-ducking than an investigative procedure, an immersion in public scrutiny which is as prone to failure (and impure voyeurism) as its medieval forerunner