Under South Africa's security laws, it was not unusual that black student leader Peter Mokgoba was arrested and interrogated for 12 days in May, only to be released without charge.
But Mr. Mokgoba's case became special when he disclosed afterward that his cell was fitted with closed-circuit television.
It was the first confirmation that the South African police have gone ahead with a plan they say is a step to reduce deaths in cells but which civil rights advocates regard as a ghastly step backward.
''Some have said that closed-circuit television in the interrogation rooms would help prevent the abuse of prisoners by police,'' said David Webster of the Detainees' Parents Support Committee, an organization opposed to detention without trial. But putting prisoners, rather than the interrogators, under constant surveillance ''is worse than physical torture,'' he added.
Prof. John Dugard of the Center for Applied Legal Studies at the University of the Witwatersrand said he suspected the police were using the cameras to ''produce further stress'' on security prisoners, so they would be more pliant.
In South Africa there have been an estimated 56 deaths of prisoners while held by police under security laws that permit indefinite detention without trial or recourse to legal representation. Civil rights advocates have found many of the deaths suspicious. They are particularly concerned about whether some of the suicides are the result of cruel interrogation methods.
In an effort to head off some of the criticism, South African Minister of Police Louis Le Grange drew up an internal ''code of conduct'' for police interrogators in 1982 and last year he announced that closed-circuit television would be introduced to reduce suicides.
Civil rights advocates said the code was toothless and lashed out at the television plan. It appeared the government had shelved the idea of putting cameras in cells.
But Mokgoba said police confirmed to him that his cell was monitored, and that all the cells were monitored on the floor containing prisoners held under security laws at John Vorster Square, the main prison in Johannesburg.
A policeman ''took me to his office. He showed me the buttons that they push and the television screens,'' Mokgoba said.
Some observers go so far as to suggest that the risk of suicides by prisoners could increase as a result of the added stress of being under camera surveillance.
Mokgoba said that after police interrogated him, he felt relatively ''free in my cell.'' But ''after being told I was being watched . . . , I was always depressed.''
Interrogation ''puts tremendous pressure on a person,'' says Frank Chikane, a black activist who has been detained in the past. ''When you go back to the cell (after interrogation), you need some rest,'' he says. He thinks that surveillance in the cell is ''going to produce more mentally affected people out of detention.''
The police would not confirm or deny that closed-circuit television had been installed.