President Botha of South Africa turned down a petition yesterday for a retrial of a black man sentenced to death in June 1983 for the murder of a security policeman, also black, seven months earlier. The convicted man, Benjamin Moloise, aged 30, a poet and upholsterer by trade, who has been in "Death Row" in Pretoria Central Prison since his conviction, will be hanged on Friday. No further appeal is possible. ...Fears have been expressed that the execution could provoke a violent reaction from blacks at a time of serious unrest. A partial state of emergency has been in force in South Africa since July 20. [Article continues to describe other instances of violent unrest.]