HUM the theme tune to LA Law and there'll be few people unable to identify the long-running TV series. Most will also go on to name several of the characters, but ask them what happened in the last series and memories begin to falter. There was a time when the saga of Los Angeles law firm Mackenzie, Brackman (and anyone else in favour at the time) just couldn't fail to please. For five years it basked in lavish critical acclaim, scored massive ratings worldwide and picked up Emmy awards like they were going out of fashion. But the past two years have seen a dramatic decline in the programme's popularity Stateside. Such has been the fall from favour that NBC has been forced to make a dramatic U-turn to prevent the series itself from being found guilty and sentenced to death. In Hongkong, LA Law is broadcast a season behind the US. The sixth series is the one which really turned America off and it starts here on Sunday (World, 9.30pm), so the jury's still out on whether Hongkong viewers will also choose to condemn. US audiences initially showed signs of revolt with the 1991 season - shown here until October 4 of last year. According to ATV World, Hongkong viewers stayed loyal for that series, the ratings consistently among the top 10 for the week. ATV World programme manager Shuen Shuen Hung is confident that will continue. ''No matter what's happened in America, this is still one of the best drama series on television in Hongkong,'' she said. Cynics may suggest that given the often mediocre English programming here, this simply means that even bad LA Law is better than no LA Law at all. Problems in the US began with the departure of popular characters Victor Sifuentes (Jimmy Smits), Michael Kuzak (Harry Hamlin), Abbey Perkins (Michele Green), and later, Grace Van Owen (Susan Dey), and the arrival of several new faces. Some of the newcomers, in particular fast-talking Tommy (John Spencer) and the delightful CJ (Amanda Donohoe) a chic bisexual, were equally interesting as their predecessors. But others, like sassy entertainment attorney Susan Bloom (Conchata Ferrell) and slimy Frank Kitteridge (Michael Cumpsty), came in without so much as a by your leave. AND went: Bloom and Kitteridge will be missing from Sunday's pilot, having lasted just one season. Unfortunately, so will CJ, who apparently proved too unconventional for network primetime in the US. Character recognition is not the main problem, however - after all the likes of Richard Dysart, Corbin Bernsen, Jill Eikenberry, Michael Tucker and Alan Rachins, have all been mainstays since the show premiered in 1986. The most common complaint in America is that new writers have allowed the show to stray too far from its original mix of comedy and courtroom drama. Remember when those opening lines, ''Previously on LA Law . . .'' meant serious courtroom battles counter-balanced by quirky personal asides, such as Kuzak dressing as a gorilla to woo Van Owen, or Stewart winning back Kelsey with the help of a mysterious sexual manoeuvre, the Venus Butterfly? The series we're about to see has them taken over by inter-office battles; political climbing (Blair Underwood), careers in movies (Bernsen) and sexual problems brought on by being beaten up in the LA riots (Tucker). NBC's rescue efforts have included bringing back William Finkelstein, a writer and producer on the show during its award-winning years. He returns as executive producer. His stated aim is to return to basics: the pertinent cases, the banter and most of all to get back into the courtroom and away from the distractions. He's got a lot to do if the series is to be saved. This was indicated in NBC's promotion for the current series in the US, which basically amounted to an admission that its judgement had been at fault. ''Remember when LA Law was your favourite show? From tonight, it will be again.'' It's Hongkong's turn to play judge and jury on the sixth series from Sunday. If the first episode is an indicator, then it's certainly not all bad, and given the alternatives here, we can't afford to say ''case dismissed''.