A FORMER policeman kidnapped a teenager to prevent her testifying against him in court, it was alleged yesterday. Cheng Yu-yin first threatened to burn down 16-year-old Ngai Kong-ling's home and disfigure or kill her, Deputy Judge Day of the District Court was told. Later she was allegedly kept prisoner in a locked flat for two nights so she could not attend the trial. Cheng, 24, denied two charges of falsely imprisoning her and one of perverting the course of public justice. Prosecutor Patty Lee said Cheng was originally scheduled to face trial for an undisclosed matter on December 1, 1992. But after the prosecution witness failed to attend to give evidence the hearing was adjourned for almost seven months. On June 16 the following year, the teenager was found at a private brothel in Yau Ma Tei, Ms Lee said. She told police Cheng had confronted her and demanded a talk on November 30, 1992. Kong-ling reluctantly went to a cafe with him where he threatened her, the court heard. ''He warned her not to testify against him in court or else he and the other co-defendants would burn her house and employ someone to kill her,'' Ms Lee said. Three men joined Cheng and Kong-ling was driven in a van to a flat where she was kept for five hours, the court heard. She was later escorted to another flat where she spent the night against her will guarded by Cheng, Ms Lee said. The following morning, the day of the trial, she had awoken to find three girls watching over her. ''The defendant maintained he would be acquitted as long as she did not turn up in court,'' Ms Lee said. On December 2, Kong-ling had persuaded her guards to let her out and managed to escape. She had taken refuge with friends before being found by police. The trial continues.