A second key witness testified Wednesday that he was slapped and punched by an enraged Winnie Mandela, who wanted him to confess to having homosexual relations with a white church minister.

Tabiso Mono, speaking through an interpreter, said he was badly beaten by Mrs. Mandela and her followers in December 1988 after being taken away from a church home with three other young men."She hit me with her open hands and fists on my face," Mono testified. Mrs. Mandela is on trial on kidnapping and assault charges.

Asked by the prosecution to give details, Mono told of being beaten with a whip, and being kicked and punched.

"I was assaulted. I was lifted into the air and left to drop down . . . They were trampling on my body," he said.

Another key witness, Kenneth Kgase, gave a similar account of the assault during testimony last week.

Mrs. Mandela and three co-defendants are charged in connection with an alleged December 1988 attack on Mono, Kgase and Gabriel Mekgwe. A fourth victim, Stompie Seipei, was later killed, and Mrs. Mandela's chief bodyguard, Jerry Richardson, was convicted in the death.

Mekgwe, who was also to testify, disappeared as the trial began last month.

Mrs. Mandela, wife of African National Congress leader Nelson Mandela, says she is innocent.

Following Kgase in the witness box, Mono said he and the three others were taken from a Methodist Church home to Mrs. Mandela's house. He said they were questioned about having homosexual relations with a white minister and Seipei was accused of being a police informer.

Mono testified that Mrs. Mandela questioned them about the accusations, then beat them. He said Mrs. Mandela had said, "You are not fit to be alive."