A key member of a vice ring which bribed police officers agreed to become a Crown witness - but then tried to manipulate a fellow witness when the case came to trial. Cheng Sui-wah, who had been granted immunity, was yesterday jailed for five years for bribery and perverting the course of justice. The Mongkok villa owner was part of a vice syndicate which paid off officers from April to October 1993, the District Court heard. The ring was broken on November 9, 1994, and Cheng agreed to testify in the trial of a policeman. But on February 26 this year, he approached another Crown witness - brothel boss Cheung Tak-loi - and asked him to alter his evidence. Cheng, 39, was found guilty of conspiracy to bribe former police inspector Lai Kin-keung and perverting the course of justice. Deputy Judge Li Wai-chi ordered Cheng, who had denied the charges, to return $100,000 he had received from the vice syndicate.