"Penitentiary," a film now playing at several local theaters better known for showing Bruce Lee pictures, is the story of an innocent man who is sent to prison. By the time he has punched his way out, the viewer can't help wondering whether even guilty people should be sent to prison.

Exactly who should be sent to "Penitentiary" (within the limits of its "R" rating) is problematic. For a film that dwells, sometimes obsessively, on the themes of violence and homosexual rape, it is surprisingly innocuous -- essentially honest in its portrayal of prison life, though it does include a few cliches, a bit of broad caricature, and some highly improbable coincidence and fantasy. What it does best is stir the adrenalin in some remarkable fight scenes.

Perhaps its primary audience should be young men who are considering crime as a career. The shock of some of the early scenes, in which the hero (played by Leon Isaac Kennedy) is taken first to a county jail and later to a long-term penitentiary, might motivate them to enter a monastery instead.

In the county jail, one inmate is wandering around with his hair standing on end, a glazed look in his eyes and a lighted cigarette smoking in his left ear. He is looking for a fight or a fix or perhaps a quick roll in the hay. Down the cell-block a bit, someone is crawling on hands and knees and barking like a dog -- his way of looking for the same things. Violence breaks out for reasons that are never clearly established, and the atmosphere is similar to some of the climactic moments of "Marat/Sade," only perhaps a bit more tense.

The penitnetiary is worse. Kennedy runs afoul of a group of inmates known collectively as "The Beasts," who see him entirely as a sex object, and he is locked in a cell with one of them, a gangling, gap-toothed, muscular brute who boasts, "I don't box -- I kill" and begins to make sexual advances.

The fight scene in which Kennedy defends, as it were, his virtue, is prolonged, intense, magnificently choreographed and filmed, and remarkably varied considering that all the director has to deal with are two men in a prison cell. Those who have a taste for violence may find this scene alone worth the price of admission.

But it is impossible to fill 90 minutes of film interestingly with nothing but fighting and homoerotic obsession, and "Penitentiary" begins to run into trouble when writer-director Jamaa Fanaka finds it necessary to vary his plot lines.

Becuase the chief guard's brother-in-law is a fight promoter who shops in the prison for new talent, Kennedy decides to enter a boxing tournament and win a parole. This comes eventually, but an intermediate prize is a session with a prostitute -- coincidentally, the same prostitute who originally got him into the fight that landed him in prison. While the tournament is going on, some of the inmates manage to arrange quick encounters with inmates from a women's prison next door, and a good time is had by all -- except those who get beaten in the ring or knifed in a grudge fight later on.

"Penitentiary" makes a serious and nearly successful attempt to rise above the sex-and-violence genre and make a serious statement about prison life. The effort is commendable, but the best parts are still the scenes of sex and violence.