On the wall of Jimmy Kruger's study in his Pretoria home is a grouping of five pictures, beginning with his election to Parliament in 1966, his first Cabinet appointment and each elevation up to his current position as South African Minister of Justice. At the top is a conspicuous vacancy.

But James Thomas Kruger, 60, is unlikely to fill the position for which that space has been saved, the premiership. In fact, Kruger's entire career is now on the line because of the controversy over the death in police detention Sept. 13 of Steve Biko, the founder of South Africa's black-consciousness movement.

The issue of detainees dying in police custody has been building for 18 months - since the death of Joseph Mduli in March, 1976, within 24 hours of detention by security police. Pathologists said Mduli's body suffered "extremely congested" brain hemorrhages, three broken ribs and severe bruising on the head, neck and stomach. Four policemen - two black and two white- were subsequently tried, but acquitted.

There have been 20 subsequent deaths in detention. Now there is mounting evidence that the latest, Biko, also died of multiple brain and body damage, according to well-placed sources here.

With each death, suspicion has grown among South Africans, black and white alike, about police treatment of prisoners. Biko's death was the last straw for many, including government supporters and, reportedly, some government officials.

The anger is now being aimed directly at Kruger, even though most people acknowledge that he probably had no direct involvement in the detainee cases. Under law, however, the minister of justice, police and prisons is responsible for the treatment of prisoners in his custody - which puts Kruger in the hot seat. Since Biko's death, a serious campaign has been launched to oust him.

Although the National Party government has never relieved any Cabinet official since coming to power in 1948, Kruger may find that public feeling against him is running so high that Prime Minister John Vorster's government will be forced, at a minimum, to shift him to another position after South Africa's Nov. 30 general election.

In many ways, the justice minister is the ultimate Afrikaner, typifying the little man who made good, one who does not want to have his position jeopardized by those he considers not up to his standard.

Born in the Orange Free State, the heart of Afrikanerdom, he struggled to change his early life as a mine-worker by studying law at night. He worked hard as a volunteer for the National Party for 30 years before running for Parliament.

After six years of hard work in the background, he won a deputy ministership. His career continued upward as his name became prominent on the list of possible successors to Vorster as prime minister.

His personal lifestyle reflects his total immersion in the Calvinist Afrikaner culture. He regularly attends one of Pretoria's Dutch Reformed churches. Like all good Afrikaners, he loves his rugby, braaivleis (South African-style barbeque) and biltong (sticks of dried meat).

During rare vacations, he prefers to get out in the bush to hunt, probably much like his ancestors in South Africa, who go back nine generations. The rug in his study is the skin of a zebra he shot. He encourages his wife, Susan to carry on writing novels in Afrikaans, saying that there is not enough Afrikaans literature.

Like many Afrikaners, he takes a paternal attitude about the country's 18 million blacks, arguing that the white man knows what is in the best interest of the Africans.

"There is no other option of a solution to our problems but separate development. We will have to learn to love this policy - all South Africans, black and white - and love it, warts and all because there is no other option. The only other possibility is one-man, one-vote, and a multiracial Parliament," he told a Johannesburg Sunday Times interviewer last year.

In that type of system, he said, "you'll have the white man in a minority position with the whole of the economy and the infrastructure in his hands and you will find sabotage on a scale that you have never seen."

The campaign against Kruger in the Biko case flared from a series seemingly inconsistent or insensitive statements.

At the National Party congress in Pretoria two days after Biko's death, reported at the time to have resulted from a hunger strike, Kruger said. "I am not glad and I am not sorry about Mr. Biko. He leaves me cold," Kruger later said the statement, in Afrikaans, was misinterpreted, that what he meant was that he did not know Biko and could not have strong feelings either way.

At the same meeting, Kruger supported a party member's contention that a person had a democratic right to starve to death, adding, "If a man goes on a hunger strike you cannot force him to eat," a statement that infuriated many blacks. Kruger gave no indication until the next day that the prison had indeed tried to feed Biko intravenously.

Even some moderate newspapers said Kruger did not appear to know what we going on in his own department when he and his deputy put out conflicting statements on where the black leader died.

A week ago the minister made an apparent rollback, claiming he had never said Biko died of a hunger strike but only that Biko had gone on a fast a week before his death. For four days, however, Kruger had not refuted local and international press reports that the hunger strike was the cause of death - leading to new doubts expressed in local papers over the minister's credibility.

Kruger is probably the most powerful minister of justice in the Western world. He has the power to detain anyone - without charges - as long as he deems necessary. He has the power to cut off an individual from society by house arrest or a process called "banning" - again without ever explaining why.

All that power is the root of the problem, a point made by the opposition justice spokeswoman, Helen Suzman, at a "Remove Kruger" rally on Monday: "I accuse the minister of prisons and police of abusing the power he was so misguidedly given by Parliament when it passed that miserable Section Six of the Terrorism Act," which allows detention without trial.

"He has interpreted it in the widest possible way and he had allowed his security police to use the mighty weapon of Section Six in the most unbridled and unlimited way in hundreds of cases where the most demanding procedures of the normal laws of the land could and should have sufficed," Suzman said.

She added: "I accuse the minister . . . of jeopardizing South Africa's claim to be numbered among the civilized nations of the world. He has forgotten Churchill's dictum that the standard of a country's civilization is measured by the way in which it treats its prisoners."