TELEVISION / Barking up the wrong tree?: Thomas Sutcliffe on a case to answer in The M50 Murder; plus US import Pacific Station

Ghastly though it is to say it, the murder of Marie Wilkes was peculiarly suited for television reconstruction. Having broken down on the hard-shoulder of the M50 she left her child and young sister in the car and walked about half a mile to an emergency telephone. She contacted the emergency services but was put on hold while they called home to inform her family. When the operator returned there was no answer. The M50 Murder (BBC 2) used a recording of his subsequent puzzled inquiries ('Mrs Wilkes? Hello . . . Mrs Wilkes?') over a shot of a dangling phone to underline the poignant melodrama of the timing, of a woman attacked at the very moment she waited to speak to those who would have helped her.

That dark irony, and the fact that she was seven and a half months pregnant at the time, fuelled public disgust over her killing and (Tim Rogers' report suggested) placed a particular pressure on the police to find the culprit. This they did, arresting a Welsh night-club bouncer called Eddie Browning, who was eventually convicted of the crime and sentenced to life imprisonment. His appeal was turned down.

Last night's film proposed that this was an 'unsafe conviction', a slightly awkward rallying cry for a miscarriage of justice documentary, translating as it does in the popular mind into 'he might have done it, but they didn't prove it'. I suspect that the average viewer doesn't give a toss one way or the other about procedural irregularities provided they think that the right person ends up being punished. But in the event The M50 Murder was more determined than its subtitle suggested, putting forward several strong arguments against Browning's conviction.

Most of these were complicated or ambiguous - an elaborate reconstruction of the time it would have taken him to drive to the murder scene which only proved his innocence if you accepted that two witnesses (one of them his stepmother) had accurately remembered times to the minute; a videotape of a policeman under hypnosis giving evidence that apparently contradicted his incriminating evidence in the dock; the exonerating recollections of an eyewitness who had never been called in court. All of these however were subject to the vagaries of faulty memory or wishful thinking.

They also constituted 'new evidence' - the proudest boast of such investigations. But the most convincing argument in the film was neither new nor evidence at all. It was an absence, a dog that didn't bark. Despite the fact that Mrs Wilkes was bleeding heavily by the emergency telephone and despite the fact that the prosecution case depended on the fact that she had then been taken in Browning's Renault to the point where her body was left, not a drop of her blood, not a fibre from her clothes, not a fingerprint was found in the car. Recent miscarriages have taught us to be wary of the presence of forensic evidence. Oddly enough its absence, when you know that the police scientists will have left no seat-cover unturned to find it, carries far greater weight.

Pacific Station (C 4), a new sit- com about a Californian police station is a gag-rich character comedy in which the sardonic Robert Guillame plays a career detective teamed up with a blissed-out weirdo (he thinks a stake-out will be 'like an encounter weekend'). Absolute formula stuff, but very funny.