The South African government's case in the inquest into the death of black leader Steve Biko suffered another setback today when the testimony of a police official was challenged.

The government has contended that police thought Biko was faking illness in the days just prior to his death Sept. 12 in a prison hospital, a position stated at the start of the inquest three weeks ago by Col. Pieter Goosen, head of the security police in Port Elizabeth where Biko was initially detained.

Today the inquest was shown a telex memo dated Sept. 16 in which Goosen told his superiors that an injury had been "inflicted" on Biko six days before his death.

Goosen's memo, which was introduced by the Biko family's lawyer also states that Biko appeared to be in a semi-coma when he was driven 700 miles to a Pretoria hospital on the day before he died.

In Goosen's original testimony he said he had never sent any telex messages regarding Biko to his superiors. He did not mention any injury to Biko that he was semi-conscious during the trip.

The colonel was brought back to the stand today and said he thought he had originally testified that he did not remember details surrounding Biko's death and that he thought he had given information to his superiors by telephone.

He denied today that any injury had been inflicted on Biko. Rather, he said, the word "inflicted" had been used to indicate that Biko had possibly been injured during a scuffle with police interrogators.

"Inflicted" was only a play on words, Goosen said, adding that a telex message could only capsule highlights of an investigation and could not go into too much detail.

Goosen's message was recently made available to the Biko family lawyer, Sydney Kentridge, by Brig. Gen. C. F. Zietsman, head of South Africa's security police. Kentridge has been trying to enlarge the inquest into an investigation of how senior police officials obtained information about Biko's death and passed it on to Minister of Police Jimmy Kruger.

The lawyer wants to determine what was behind the initial police account that indicated Biko's death was caused by a hunger strike.

Kentridge said at today's hearing that Gen. Zietsman was told that Biko refused to make any statements admitting that he had helped put out an antigovernment pamphlet. Kentridge said this contradicted testimony from police Maj. Harold Snyman, who had told the inquest that Biko had made such a statement.

Kentridge and the counsel for the police, Attorney General Retief Van Rooyen, are to make their summary statements Thursday and Friday. The magistrate is expected to present his findings on the cause of Biko's death shortly thereafter.