SOME of Hong Kong's worst sex offenders are to be interviewed in a bid to understand their psychological makeup - and to find an effective treatment programme for them. Li Shing-fu, an associate professor in the Department of Applied Social Studies at Hong Kong Polytechnic University, will interview about 50 prisoners in a bid to discover why they commit the crimes they do. It is believed to be the first time sex offenders have been interviewed in Hong Kong for academic research. Entitled 'Psychological and Criminological Features on Violent and Non-violent Sex Offenders', the study aims to find out their character and the process through which these features are formed and strengthened. Another aim is to design a correctional treatment programme. Professor Li, a psychologist with six years experience in the Correctional Services Department, will not only speak to rapists, but also non-violent sex offenders, such as peeping Toms. He will also conduct studies on their family backgrounds and relationships. He would not say whether the territory's most infamous sex offenders, including the Tuen Mun rapist Lam Kwok-wai, would be interviewed. In his earlier report, he said the causes of Hong Kong sex crimes were many. Sex offenders did not commit the crimes out of curiosity, or to gratify momentary impulses, he said. On the contrary, Professor Li said, many of the offences were habitual in nature and were premeditated. More often, Hong Kong rapists wanted to control the victims, with many of them being triad members. Offenders often did not achieve sexual satisfaction, he said.