South Africa's security police were exonerated of any crimial, responsibility for the controversial prison death of black activist leader Steve Biko by a Pretoria magistrate today.

Marthinus J. Prins, who presided over a three-week inquest into Biko's death Sept. 12, said Biko died of head injuries suffered during a struggle with police. He added, however, "available evidence does not prove the death was brought about by any act or omission involving an offense by any person."

Testimony at the trial had described how Biko had been kept in iron shackles, made to lie on a urine-sodden mat and driven 700 miles in a Land Roverwhile in a semiconscious state.

Only eight hours before Prins announced his findings, security police arrested Biko's brother, Kaiyo, and his cousin, Solomon, and nine other persons in a raid on the Soweto home of an Anglican preiest, according to the Biko family lawyer, Shun Chetty.

Security police in Soweto refused to confirm or deny the arrests. In formed sources said, however, that the police were trying to find some pumphlets being printed by members of the Soweto action committee. The committee is an ad hoc group formed after the government banned many black organizations Oct. 19.

No South African secuirty policeman has ever been successfully prosecuted for the death of a prisoner although 41 persons have died in detention sice 1961, 21 in the last 21 months.

Nevertheless, Prins verdict is ecrtain to further worsen the already tense relations between blacks and whites in the country, Critics of the governments policy of racial separation say it will be interpreted as a license for the security police to act with impunity towards detainees, who are mostly blacks.

Biko had sturacted international attention for his contention that blacks in South Africa had to develop pride in themselves before they could make any significant change in the government.

The domestle fouror following his death led the government to suppress 17 black organiazations and detain 40n entics of its racial policies on Oct. 19. This further inflamed international opinion and led the United National Security Council to impose a mandatory arms embargo on South Africa Nov. 4.It was the first time the United Nations had ever imposed sanctions on a member courtry.

The packed gallery at the magistrate's court, which included Biko's wife. Ntsiki freeded Prins' verdict today with silence and quickly went outside where a group of about 50 blacks chanted. "They have killed Steve Biko. What have we done? Our sin is that we ae black." About 200 persons in a bitter mood milled about for about an hour but there were no incidents.

Sydney Kentridge, who represented the Biko family at the inquest was not a t the court but he said later that bar rules would not allow him to comment on the findings.

Under South African law, there can be no appeal from an inquest rulling. There is the possibility of a review. This procedure, however, is rarely followed in South Africa and is only possible when there is a clear and abvious irregularity in the findings.

The hearing, with its revelations of the treatment given Biko, threw a powerful spotlight on the conditions awaiting political detainees in South Africa. According to the South African Institute of Race Relations there are 714 such detainees in the country.

The Biko family could initiate a civil suit against the sevurity police but they have not announced plans to do so. Mrs. Biko, a nurse,has two children.

Brig. Gen C.F. Zeitsman, hte head of the security police was asked if there would be any administrative reprimand of the eight officers who had dealt with Biko during his detention. He said he could not discuss the matter outside his department.

In August 1976, four security policemen in Durban were charged wit the death of a detainee but they were azquitted since it could not be determined that they were personally responsible for the fatal injuries.

[TEXT OMMITTED FROM SOURCE] think twice before acting against South Africa.

"Small as we are, our people. Afrikaans an English speakers, will defend South Africa to the last person, if it is necessary, in fact, to do so" he said.

"I think this is the masage that has gone to the world outside in no uncertain terms."

Vorster said he was not planning an immediate Cabinet reshuffle.

"It is not lkiely that the Cabinet reshulfle will come before February," he added.

Earlier today, veteran opposition leader De Villiers Graaff said the National party's landslide victory had left the opposition "impotent and largely rirelevant."

De Villiers, 65, president of the New Rebublic Party, which was reduced from 23 to 10 seats in Wednesday's election, said the ruling party's triumph was due to polarize the white voters.