Two teenage girls helped strip a 15-year-old girl who was then photographed nude, a court was told yesterday. Some of the pictures were posted to the alleged victim's former school after her mother refused to pay $600,000 for them, the District Court was told. Waitress Chan Yee-yan, 18, and student Hui Pui-yee, 16, deny aiding and abetting an indecent assault on a woman. Chan also denies blackmailing the mother with two men, known as Ah Fai and Ah Hang. The defendants met the girl in July last year through a mutual friend, said prosecutor Paul Chiu. One night, the group went to a karaoke lounge in Tsim Sha Tsui and then moved on to an amusement arcade where Pui-yee and Ah Fai gave the victim a tablet, he said. The girl fell unconscious and woke up on a bed in a Mongkok villa, Mr Chiu said. Two months later, her mother received a telephone call from a man who claimed he had nude pictures of her daughter and demanded $600,000 for their return, the court heard. When she refused to pay, the man threatened to display the photographs around the girl's home and school, it was claimed. The school principal testified yesterday that she had received five nude photographs of the alleged victim on October 23. She alerted police and an investigation led to the arrest of the two defendants. Under caution, Pui-yee told the police that Ah Fai ordered them to take off the girl's clothes, while Ah Hang took about 20 photographs. The alleged victim failed to turn up in court to testify yesterday. Deputy Judge Li Wai-chi adjourned the case until Monday.