A U.S. law school dean who was asked by the American Bar Association to attend the inquest into the death of Steve Biko has concluded that the South African black civil rights leader died as the result of a beating during interrogation by South African security police.

That finding is contained in a report, made public yesterday, by Louis H. Pollak, dean of the University of Pennsylvania law school and former dean of the Yale law faculty.

Pollak's conclusion contradicts the ruling of the South African magistrate, M.J. Prins, who presided over the three-week inquest in Pretoria last November and December.

Prins found that Biko, who died last Sept. 12 while in police custody, suffered head injuries that were the likely cause of his death. But he also ruled that the injuries apparently were inflicted when Biko allegedly attacked police interrogators a few days earlier.

However, at a press conference here yesterday, Pollak charged that the evidence and testimony at the inquest did not beat out the magistrate's finding. While conceding that his own conclusion about Biko's death was "arguable and subject to debate," Pollak said:

"At the very minimum, we could not responsibly reach the result that the magistrate reached. At the very minimum, the magistrate had to say, "The evidence does not tell me what happened to this man, and further investigation is required.'"

pollak attended the inquest as a representative of the ABA's Section of Individual Rights and Responsibilities and of the Lawyers' Committee for Civil Rights Under Law, a U.S. organization that has provided legal aid for South African rights activities.

However, Pollak stressed that the report represents "solely my own findings as an observer for these organizations" and does not have their official endorsement.

He also noted that, because of difficulties in obtaining a visa, he was able to attend only one week of the inquest sessions. For the rest, Pollak said, he was forced to rely for information on transcripts of the hearing, press reports and interviews with the Biko family's lawyers and others who were present at the sessions he missed.

In particular, his report places heavy reliance on the findings of Sir David Napley, a former president of the British Law Society. Napley attended all but three days of the sessions and. in December, wrote a report reaching essentially the same conclusions as Pollak.

As stated by Pollak, they are that Biko, who was arrested last Aug. 18 and held incommunicado on suspicion of terrorist activity, was at some point beaten by the police in an effort to make him talk.

Pollak says he believes the police did not intend to kill Biko but inadvertently injured him in a way that caused severe brain damage. The injuries, his report charges, were aggravated by the failure of the police first to provide Biko with adequate medical care and then transporting him 750 miles in the rear of a Land Rover to a hospital where he died.

To back up his findings, Pollak argues that the hearing record is filled with contradictory and, in some cases, dishonest statements by the police. In particular, he says, none of the police testimony established in a clear fashion that Biko received a severe head injury during the scuffle on Sept. 7 when he allegedly attacked his interrogators.

Instead, the report charges, the evidence provides strong grounds for assuming that Biko was beaten in some other way, that the police tried to cover up his injury by telling doctors that he was feigning illness and that, after his death, the police failed to conduct a thorough investigation into the circumstances.

At his press conference, Pollak described the prison doctors who initially attended Biko as "the most pathetic and most contemptible human beings I have ever seen. In their testimony at the inquest, they made clear that they approached Biko not as a patient but as some piece of apparatus presented to them by the police for repair."

However, Pollak said it was his impression that the inquest, despite the limitations placed on its scope and the inadequacy of the verdict, was conducted in an impartial manner, with lawers for the family being given wide latitude to state their case.