In death far more than in life, Steve Biko is casting a long shadow across this racially troubled land.

The still sun explained death of the 30-year-old black leader in prison on Sept. 12 has more than ever put the South African system of Justice - with its provisions for unlimited detention without trial or charges, its sweeping Terrorism Act, and its apparent use of brutal assault and torture - on international trial.

For opponents here and aboard of South Africa's universally condemned system of apartheid, or strict racial segregation, the issue probably could not come at a better time. The Carter administration has more human rights a central concern of its foreign policy and Amnesty International has just won the Nobel Peace Prize for its crusade for the same cause.

In this atmosphere, South Africa risks seeing all its best efforts at making changes overshadowed and international attention diverted to the very worst aspects of its racial policies.

Even top government officials now adult privately that the implications of the "Biko affair" are, as one of them put it, "bad, very bad" for South Africa. "We are trying to see that this kind of thing does not happen again," he said, without making the slightest attempt to defend what happened.

Jimmy Kroer, minister of justice, has gone so far as to indicate that his policy may have been partly at fault and his prison doctors negligent. But he is still steadfastly defending his force against charges of torturing or assaulting detainees, although he did admit in an interview with Time magazine this week that "I have not got all the facts."

The impact of Biko's death on internal politics is mounting. In fact, the whole affair has become entangled in a long-standing struggle between the liberal English-language press, led by the Daily Mail and the black newspaper, The World, and the National Party government over the issues of justice and press freedom in this country.

At first, most whites here had no idea who Biko was or what the international outcry over his death was all about.

Now, as each day passes without the government releasing the findings of its post-mortem report, demands are multiplying for a public inquiry not only into Biko's death but also into more than 40 other similarly suspicious cases over the past 14 years.

The government will probably head off this campaign by agreeing to an official inquest only in the Biko case. The pro-government English-language daily, the Citizen, has predicted that such an inquest would begin this week and that Kruger and the government would ultimately be vindicated of allegations in the English-language press of police responsibility for Biko's death.

Civil rights advocates here contend that many political detainees undergo some form of police assault or torture and that the growing number of deaths in detention are not suicides or accidents as the police keep insisting.

Trying to get their case put before the white public, however, has not been easy. Earlier this year, a publication of the Christian Institute entitled "Torture in South Africa?" was banned, despite the fact that it contained only a collection of information that had already appeared in local newspapers and periodicals.

Now, however, the same issue is being raised in various quarters in a different form. For example, a small but growing number of lawyers, jurists, students, newspapers, and civil rights groups are demanding a national public inquiry into the laws of the country that have led to the death of 41, 44 or 47 detainees - the estimates vary - since 1963, 20 of them since March of last year. Members of the dominant Africaner elite have joined English-speaking South Africans in the demands.

Last week, the South African Institute of Race Relations issued a 70-page booklet - Detention Without Trial in South Africa, 1976-1977 - reviewing the evidence surrounding the latest deaths of detainees and warning that the government's misuse of its own security laws are driving the black opposition into increasingly covert "extra-parliamentary political action."

"It is essential to acknowledge that structures are not provided for the majority of the population to express their political aspirations," the institute said. It also raised the question of whether the country's drastic security laws were not being misused even to crush peaceful black efforts to imporove their lot, such as the current campaign for better education.

The institute said that 662 persons were being detained without trial as of Sept. 30, the highest number at any one time since the first laws allowing this practice were introduced in 1961. Since the beginning fo the current black protest movement in June, 1976, a total of 2,430 persons has been detained under the Terrorism Act, according to the publication.

The Institute concluded that until all provisions for detention without trial are abolished and South Africa returns to the rule of law, a major stumbling block will remain on the path to peace in the country.

It called for a full judicial commission of inquiry into the whole system of detention without trial and of police abuses under it.

South Africa has a bewildering array of security laws allowing the police, among other things, to detain for months, and even years, any individual who is even vaguely suspected of being involved in activities aimed at changing the system by force. They can also detain anyone who might serve as a state witness and this appears to have become a common practice.

The epitome of what white and black opposition leaders regard as the worst features of the South African system of justice is the Terrorism Act of 1967. This allows for unlimited detention simply to interrogate a suspect and no access to the detainee by anyone except a police officer or the justice minister.

The term "terrorism" is defined by the act in such general terms that anyone involved in any kind of action that wittingly or not endangers law and order or stirs up hostility between the races is labeled a "terrorist." Furthermore, the accused is presumed guilty "unless it is proved beyond a reasonable doubt that he did not intend any of the results of 12 different kinds of possible offenses including "to embarrass the administration fo the affairs of the state."

Among the array of South African laws and practices, however, the two main targets of criticism are unlimited detention without trial and the use of torture to extract confessions or information from detainees.

Biko, for example, is widely suspected in white and black opposition circles of having been beaten by his interrogators, during which he received a blow on the head that resulted in his death.

Sworn testimony and affidavits of various black and white detainees, including a startling number of so-called "state witnesses," have alledged the use of the following tactics by police to force confessions or information from them:

Bodily assault with fists and clubs.

Long periods of standing, two days and more without sleep, food or even permission to go to the bathroom. Sometimes gravel is put in the detainee's shoes to make him or her more uncomfortable.

Long periods of solitary confinement, even for state witnesses. In a trial involving Biko earlier this year, the state produced a 14-year-old youth who had been in such confinement for a month. He was so weak and dizzy in court that he asked to be allowed to sit down.

Electric shock treatment applied to various parts of the body, including the penis.

The tying of bricks to men's testicles.

Three other techniques have been given the names of "the barrel," "the airplane" and "the imaginary chair." The first involves whirling person whose hands and feet are tied around a bar stuck behind his back; the second, throwing the detainee high in the air and allowing him to land on the cement floor, and the third propping up the accused against a wall in a sitting position without a chair under him. If he slips, he is hit and forced to stay in that position for hours until he talks.

The South African authorities repeatedly denied all allegations of the use of such methods and proudly point to the failure of any South African court to convict any policeman of such abusive treatment. This is apparently literally true, but there have been a number of out-of-court settlements of cases involving allegations of torture and various judges have indicated skepticism about police accounts of how detainees died.

Indirectly, South African officials have sought to justify harsh methods of interrogation by arguing that the country faces a determined effort by some black militants to promote revolution and overthrow the state by force. In fact, there is every indication that urban guerrila warfare is beginning in South Africa; a number of black nationalists have been caught either attempting terrorist acts or while hiding with arms or explosives in black townships.

Civil rights advocates here fear that the use of such tactics by black militants will only lead to worse abuses by the police of the security laws, with more and more innocent detainees suffering the consequences. They already allege that in the majority of torture cases the accused were not involved in any illegal activities.

They feel the increasing resort to torture is becoming counterproductive and only serving to further alienate the entire black population. "In how many cases in history has torture been crucial to the survival of the state anyway," said one civil rights defender.

"Surely it is important we do all we can to protect the innocent who are being detained reather than give the police a free hand as urban terrorism escalates."

Still, there is little optimism in civil rights circles here that the Biko case will result in any reforms. In fact, the talk in these quarters is of a new admendment to the Terrorism Act to include a mandatory death sentence for anyone found in possession of arms or explosives from outside the country.

If this is the case, and the advent of urban warfare seems to make it increasingly likely, then the outside world seems destined to see more executions of blacks and more repression in South Africa rather than less. "After all," noted one Afrikaner intellectual, "the whites feel they are now in a struggle for their very survival. What do you all outside expect."