Updated at 3.05pm: A High Court judge on Monday warned a serial rapist who launched attacks on three young students and captured the rape scenes on video that he would be facing life imprisonment. Deputy Judge Alan Wright told Cheung Lai-man, 34, that he has this sentencing option in mind but reserved his decision until obtaining two psychiatric reports on the defendant. Cheung pleaded guilty to three charges of rape on three students, aged 12, 20 and 21 between 1997 and 2001. The offences took place either in the bushes or at the hillside in Tseung Kwan O and Sha Tin. He denied another rape on another girl in 1992 and two charges of robbery. The prosecution agreed to leave the charges on court file. Prosecutor Arthur Luk Yee-shun told the Court of First Instance that the defendant who was masked with a balaclava and wore gloves, ambushed the three victims while they were on their way to school. He threatened the girls with a knife, tied them with a metal chain and blindfolded them before launching the attacks. He recorded the three rapes on video and the tapes of which were found in a safe at his marital home in Tsuen Wan. Deputy Judge Wright adjourned the case until October 7 pending psychiatric reports.