In any season, "The Biko Inquest" would command attention, but with the current turbulence in South Africa, it is particularly -- indeed, sickeningly -- timely.

Using actual testimony, this documentary play recreates the three-week inquiry by a South African court into the ambiguous death of black activist Stephen Biko in 1977, while in the custody of the South African police. At the end, the judge absolves the police and medical officials of any wrongdoing. Viewers of the play, to be telecast tonight (at 8 p.m. on Showtime), are likely to arrive at a different conclusion.

Taped last year in Britain, the no-frills production stars Albert Finney as the Biko family's lawyer, a man who knows from the start that he cannot win the case but hopes nonetheless to focus international attention on the ruthless methods of South African police. There are no moments of high drama, no surprise revelations, no sudden outbursts. Instead, the proceedings are characterized by a lot of quiet squirming and bald equivocating, as the various participants present a curiously sanitized version of bloody events.

The preposterousness of some of their assertions would be comic were the implications not so chilling. Asked, for example, to describe his interrogation tactics, Col. Pieter Goosen, the head of the security police, talks about cultivating politeness and building up trust, but then admits, "Sometimes we use sarcasm."

Biko was arrested in August 1977 for distributing pamphlets the government found subversive, and subsequently detained for three weeks in a cell in Port Elizabeth. Clamped in leg irons and transferred to a civilian office building for interrogation, he received a severe head injury sometime between the evening of Sept. 6 and the morning of Sept. 7. Later, naked, manacled and in a semi-coma, he was tossed into the back of a Land Rover and driven 800 miles to Pretoria Prison, where he died on Sept. 12.

The officials under investigation find nothing suspicious in any of that. The leg irons were for Biko's own protection, a precaution to prevent him from committing suicide. Biko, they maintain, could have injured himself during a "scuffle" on the morning of Sept. 7, when hurling a chair across the room, he went so "berserk" that five men were required to subdue him.

The three doctors called in to examine Biko are no less informative. At the time, their reports discounted the bruises on Biko's face, his slurred speech, his urine-soaked bed and his deadened leg and concluded there was nothing wrong with him. On the stand, they have no answers for their gross incompetence. The strongest defense anyone seems able to come up with is that Biko, a four-year medical student familiar with medical symptoms, was "shamming" a brain injury in order to escape further interrogation.

Beyond the shameful particulars of the case, what is horrifying about "The Biko Inquest" is the tone of measured rationality that the witnesses employ on the stand. It is a tone we continue to hear out of official South Africa, as if all this talk about racial inequity were so much nonsense. The reasonable air and the gentlemanly restraint are, under the circumstances, obscene.

To Finney falls the outrage, the indignation, the disbelief and the heavy irony, and he sounds the notes crisply. Everyone else in the cast underplays the emotions, just as the characters are trying to downplay the conditions of Biko's incarceration. Methinks, you will find yourself musing, they all protest too little.

"The Biko Inquest," which was edited from court transcripts by Norman Fenton and Jon Blair, was first performed off-Broadway in 1978. Seven years have not diminished its significance, which may be the biggest tragedy of all.