With the hysterical teacher from Big Brother and the eventually cured optimist from Tory Central Office both voted out on Friday, we had to wait but a single day to find a successor for the title of most irritating person on television. He is Gil Grissom, the lead character in CSI: Crime Scene Investigation, which started a run on Channel 5 on Saturdays (9pm). In the first, feature-length episode, Grissom (played by William Petersen) was promoted to head of the Las Vegas police CSI unit, replacing an incredibly unpleasant has-been called Brass. Captain Jim Brass (Paul Guilfoyle) revelled merely in being an asshole, however; Grissom revels much less attractively in being a saint.

"There is no room for subjectivity in this department," is how a typical Grissom homily begins. "We handle each case objectively, without presuppositions, regardless of race, colour or bubblegum flavour." (Oh yes, Grissom's perfection encompasses verbal wit: later, he knocked on a door and announced to a suspect: "I have a warrant for your toenails.") Doubting that a body had fallen voluntarily to the bottom of a high-rise hotel, he explained that, as suicide was the ultimate act of cowardice, "it's unlikely anyone cowardly enough to take his own life would be brave enough to watch his own death". Grissom's sanctimony is indecent. Restricted for reasons of economy to explain her motives in two sentences, a murderer complained that her victim had disrespected her. "I am a woman. I deserve respect." "Not any more," replied our hero.

Petersen is a subtle actor, so I assume he knows, even if his writers do not, the danger he runs maintaining this level of righteousness. I assume we shall soon discover that Grissom, while without flaw at work, has hidden psychological problems that manifest in his private life. He has, after all, already owned up to the character deficiency of having no children and not knowing how to behave on a date. One can assume he knows his forensics but is Bad At People. And better to be the actor playing Grissom than an actor playing anyone else on Grissom's hard-bitten, Nicorette-gum-chewing team. The rest have personalities attached to them in as rudimentary manner as Brass's clip-on tie. Catherine Willows (Marg Helgenberger): single mum, soppy-stern; Warrick Brown (Gary Dourdan): cocky, gambling addiction; Nick Stokes (George Eads): ambitious Lothario; Sara Sidel (Jorja Fox): no-nonsense brunette. And so on.

Two things make it unlikely, however, that the superficiality of these characterisations will mar our pleasure. The first is the show's frantic but confident plotting. Although the effect was magnified by Channel 5's decision to splice two episodes together to make an evening of the series's debut, there were at least half a dozen crimes being solved here, more than Hill Street Blues attempted in its heyday. What is more, each was lucidly explained, which is more than can be said for the baffling whodunnits of NYPD Blue.

The second reason we don't miss fuller characterisation is that, in this series, the science stars (much more so than in the British equivalent, Silent Witness). The zoom lens hurtles in to focus on evidence, be it a hair end, a scruff of carpet caught in a watch, or a bullet - which, very impressively, we follow from the barrel of a gun into its target's stomach. I have seen nothing like these techniques employed since Robert Winston's documentary series Superhuman. CSI's writers seem to have taken to heart Grissom's advice to his team to ignore the motives of these lying, shifty human suspects, and to concentrate instead on the great truth-teller - scientific evidence.

When DNA analysis became common, some crime writers feared for the genre lest science made every case instantly open and shut. We now know this is not the case (look at the Hanratty affair). CSI: Crime Scene Investigation pretends it is, however, and it is to the directors' credit that, in their hands, replacing human drama with the drama of science works. And to be fair, there are sparks of originality and flair in the mise en scene. It is a cliche of opening episodes for writers to introduce the audience to their dramatis personae through the mechanism of introducing a newcomer to the plot, but few will have suspected that the beautiful rookie doing the job in this case would be killed off on her first outing. (Usually, you know, in crime work, you bite the dust the day before your retirement . . .) Also, the contempt shown by the forensic scientists towards their police department colleagues is a telling sign that network television - even crusty old CBS - is belatedly authorising America's view of the country's lousy policing.

In the US ratings, CSI is closing in on ER, and it is easily Channel 5's best import so far. But never forget that it is a creature not of Steve Bochco's, but of Jerry Bruckheimer's, the brilliant moron behind Armageddon and Pearl Harbor. I bet it was he who insisted on the series's tautological, follow-my-lips title, and I bet no one dared tell him that its elements needed to be divided by brackets rather than a colon. NVL: not very literate.

Andrew Billen is a staff writer on the London Evening Standard