Semen found on the private parts of the body of a 15-year-old girl may have come from a man standing trial for murder, prosecutors told a Hong Kong court on Thursday. DNA tests found that the male bodily fluids found on teenager Kwok Wai-ming may belong to Lau Cheung-fai, prosecutor Martyn Richmond told the High Court. “Semen was detected in both sets of anal and vaginal swabs,” he told a seven-member jury. Lau, 37, denies murdering Kwok on December 8, 2014 in his Mong Kok flat. In his opening address on Wednesday, the prosecutor said Lau struck the cheerful and talkative “typical Hong Kong teenager” with a ketchup bottle at his home, after a private photo shoot went wrong. Richmond said Lau then wrapped adhesive tape round her face and neck, forced Chinese wine down her throat, and indecently and – at times forcibly – assaulted her private parts as she suffocated. Lau then put her body into a suitcase, the prosecutor alleged. On Thursday, Richmond said subsequent DNA tests also showed blood stains on and in a suitcase in Lau’s home may belong to Lau and Kwok. While a sample collected inside the case may have come from the girl, blood on the outer surface may be from Lau, Richmond said. A ketchup bottle on which there was DNA comparable to that of Kwok was also found at the defendant’s home. The court was earlier told that Lau dragged the suitcase to the nearby Harbour Hotel. Richmond said that it was undisputed that a staff member remembered helping Lau check in with a suitcase. The next day, the prosecutor said, Lau approached a woman working at a nearby rubbish collection station to ask for help to remove some garbage. Using a hand cart he borrowed from the woman he brought a nylon bag with red, white and blue stripes back to the station, but was unable to lift the bag. The woman offered to help, but grew suspicious after Lau left. She saw what she suspected was a body inside and told her superior who alerted the police, the prosecutor said. Officers who arrived at the scene found the girl’s head and feet covered with a black plastic bag. They arrested Lau soon afterwards at his home after tracing the hotel records, the court heard. “I know I am wrong. I accidentally killed the opposite party. I am regretful,” he told police officers after he was cautioned. Richmond said human DNA was also found on adhesive tape and hair in the hotel room, as well as blood stains on a towel. While the DNA extracted from the hair and tape may have belonged to Kwok, most of that from the blood on the towel may have been Lau’s. The court also heard Lau had been taking medication for mental conditions, including depression, schizophrenia and bipolar disorder. The case continues before Mr Justice Kevin Zervos on Friday.