The Supreme Court of South Korea has rejected an appeal by prosecutors and upheld the 23-year prison sentence for a Chinese fisherman who killed a Korean coastguard last year. The court did not accept prosecutors' arguments that Cheng Dawei should receive a longer sentence for stabbing the coastguard and seriously injuring another officer during a boarding in the Yellow Sea in December. "It's the final verdict," said Chen's lawyer, Hu Xianpang. "This case is closed." The scuffle broke out after the coastguard - carrying batons and rubber-bullet-firing guns - boarded Cheng's fishing vessel inside South Korea's exclusive economic zone in the Yellow Sea. The skipper attacked corporal Lee Cheong-ho with a knife and seriously injured another officer. It was the second time Chinese fishermen had killed a South Korean coastguard officer in less than four years. Prosecutors charged Cheng with murder and sought the death penalty at his initial trial in Incheon. The court convicted him and handed down a sentence of 30 years, but Beijing refused to accept the verdict. His sentence was reduced to 23 years after a second trial before the Seoul High Court in September, the decision upheld yesterday by the Supreme Court.