A PRISON officer was acquitted yesterday of assaulting an inmate when a deputy judge ruled he had no case to answer. Deputy Judge Yung made the ruling after Assistant Officer I Ma King-kan's counsel, Anthony Yuen, said Mr Ma had not been identified during the trial as one of the culprits. Mr Ma, 23, was on trial in the District Court with four other Correctional Services Department officers from Lai Sun Correctional Institution, Hei Ling Chau. Ma Lam-hoi, 21, who was serving 15 months for being an illegal immigrant, told the court last week he was thumped, kicked and stamped on more than 50 times by officers after he was caught fighting with fellow inmate Tin Wan-fei, also an illegal immigrant,on April 10, last year. Both men have since been released from jail. The remaining officers on trial are Acting Principal Officer Cheng Siu-kwong, 32, and Chu Siu-fai, 21, Lee Tak-ming, 24, and Chau Ming, 29, who all hold the rank of assistant officer II. Chu, Cheng, Lee and Chau face a joint count of causing grievous bodily harm with intent to Tin, 22. Chu, Cheng and Lee are also jointly charged with assault occasioning actual bodily harm on Ma Lam-hoi. Mr Ma King-kan had also faced this charge. Lee faces a further count of assault occasioning actual bodily harm, while Chu faces a count of common assault. The Crown alleged these two offences happened outside cell No 7 and that Tin was assaulted by Chu and Ma Lam-hoi by Lee. The defendants have denied all charges. Mr Gerard McCoy, representing Chu, Cheng and Lee, said the two charges of assault occasioning actual bodily harm ought to be reduced to common assault as no officer had harmed Ma Lam-hoi. He said the only harm could be an injury to his mouth, which resulted from the earlier fight with Tin. Mr Yuen, also representing Chau, said the Crown alleged the grievous bodily harm to Tin was traumatic pancreatitis resulting from Tin's abdomen having been stamped on. But Chau was not at the scene. Prosecutor Luke McGuinniety accepted Mr Ma King-kan had no case to answer. On the charge of assault occasioning actual bodily harm, he said Ma Lam-hoi was in great pain when he went to the fingerprint room. Common sense and his testimony showed actual bodily harm was done to him, Mr McGuinniety said. As for the charge of causing grievous bodily harm with intent, he said Chu, Cheng, Lee and Chau had inflicted injuries on Tin. Deputy Judge Yung will rule on the defendants today.