In taking the part of Kathleen Riley, the beleaguered public defender in "Suspect," Cher must have thought she would turn people's heads around with the potent range and diversity of her talent. The role she plays -- that of an earnest, workaholic D.C. attorney who continues to slave away for a fraction of what she could make in private practice -- is the sort that actors think of as a plum and audiences dread. It's Oscar bait, but in this case, I don't think anyone will bite.

There's a sort of reverse vanity that draws performers to parts like this, and in Cher's case, the sheer plainness of the woman is what must have first attracted her. Kathleen is a nose-to-the-grindstone type -- a drone. Her dinners are eaten by the tablespoonful straight out of a giant jar of Skippy, and late at night, after everyone else has gone home, she's at her desk poring over briefs, looking for an edge. What she needs is a break, but instead she gets saddled with a new client, who's accused of murder.

When the body of a Justice Department secretary turns up in the Potomac with her throat cut, the police poke into a drainage pipe and, huddled at the end, is a man with a beard, long hair and fierce-looking, red-rimmed eyes (Liam Neeson). Beside him is the secretary's purse, which is evidence enough for the cops to haul him in. And when a parking lot attendant claims to have chased him out of the victim's car earlier in the evening, the case against him looks pretty solid.

But the movie doesn't restrict itself to the problems of this one unfortunate man. Tangled up in the secretary's murder is the suicide of a Supreme Court justice, whom we see in the opening scene plunking a fat envelope into the secretary's palm just before putting barrel to mouth. There's a pestilence afoot in Washington, and this lost soul is the fall guy.

The accused, who, in addition to being homeless, became deaf and mute as a result of an illness picked up in Vietnam -- this must be some kind of record for fashionable afflictions -- has special case written all over him. So what if Kathleen bends a few statutes, risks prosecution and disbarment -- she cares.

Her accomplice in these extralegal activities is a slick congressional lobbyist named Eddie Sanger (Dennis Quaid). What Eddie lacks in sincerity, he makes up for in guile. Expediency is Eddie's ethic. He sits on the jury, and when he notices a detail that counsel misses, he picks up the phone and drops her a hint. And when it works once, they keep the partnership going until the case is won.

"Suspect," which was written by Eric Roth and directed by Peter Yates, makes an odd point: that perhaps, under certain circumstances, it's all right to dispense with professional ethics and indulge in a little jury tampering. Yates also skates blithely over such things as probability and common sense. This might be forgivable if the film were entertainingly made or at least energetic, but it's neither. As a thriller, its becalmed.

The filmmakers have also made a major miscalculation in making their heroine so dependent on Eddie for direction. Kathleen's problem is that her passion outstrips her brainpower. When time after time Quaid comes to her rescue, you begin to wonder how this woman passed the bar.

The character is an impossible one; I don't know who could play it. As Kathleen, Cher is trapped trying to play the one thing she's not -- dull. For the most part, the characterization is an act of self-negation; it's Cher trying not to be Cher. On occasion, she gives Kathleen a chance to sass and talk back. But she can't find anything of herself in this woman, and the performance is dogged, joyless.

Quaid, who can usually be counted on to perk things up, is only marginally livelier, but all he's doing here is a variation on the velvety charmers he's played recently, and he looks as bored with it as we are.

"Suspect" doesn't provide even the most basic pleasure that we've come to expect from thrillers -- it's doesn't get our pulse racing. For most of it, we're stuck in what must be the ugliest courtroom in the history of movies, and after a while, it becomes a drag on your spirits. It's like being trapped in a feature-length episode of "Superior Court." The clenched expression on Cher's face says it all.

Suspect, at area theaters, is rated R.