A sex-pest policeman was jailed for 16 months yesterday after his second conviction in six weeks for assaulting a teenage girl. Constable Ng Ying-wai, 24, indecently assaulted a 14-year-old after frightening her into visiting his police flat in March last year. Eastern Court heard he had served two weeks in prison last month for indecency involving another 14-year-old in his flat in December 1994. Magistrate Peter Line said it was worrying and shocking that an officer had abused his power to sexually attack young people. In the latest case, Ng, based at Castle Peak Police Station, admitted indecent assault. The court heard he met the girl and her 15-year-old boyfriend while on duty. The boy admitted having had unlawful sex with the girl. Ng let them go but warned the girl she would be in trouble if she failed to see him again at his request and at any time. He later took her to his flat. Rosaline Wong, for Ng, said his attack was out of character and he had marriage problems.