A CONSTRUCTION site worker who became the first defendant to contest DNA evidence in a Hong Kong court was yesterday jailed for four years for attempted rape. Lau Yam-chi, 43, subjected the 36-year-old victim to the sex attack after barging into her home in Hunghom on November 29, 1991, the High Court heard. The woman had been knocked unconscious. Government scientists Dr Tsui Pui and Dr Wong Dart-man told the court DNA tests showed semen found on the bed sheets after the attack matched samples from Lau. However, an expert from the United Kingdom, Dr Thomas Fedor, said the results of the genetic coding tests were unreliable. Mr Justice Bewley said the attack had ''a horrendous effect on the victim''. Lau's defence counsel, Mahinder Panesar, said he would appeal against the conviction.