Seoul High Court found Arthur Patterson, now 36, guilty of murdering Jo Jung-Pil.

A South Korean appeals court on Tuesday issued a 20-year jail sentence to a US citizen charged in his teens for murdering a Korean man nearly two decades ago.The Seoul High Court upheld a lower court's decision in January that found Arthur Patterson, now 36, guilty of murdering Jo Jung-Pil, who was stabbed multiple times with a knife in a fast-food restaurant toilet."The defendant lived 19 years of life that the victim was deprived of but did not show any sign of sincere remorse seeking pardon from the victim and the bereaved family," South Korea's Yonhap news agency quoted the court as saying.Prosecutors argued that Patterson, who was 17 years old at the time of the crime, showed a "devil-like brutality" in stabbing Jo -- a stranger to him -- to death for no apparent reason.Twenty years in jail is the maximum penalty in South Korea for an offender under the age of 18.Patterson, the son of a US military contractor, had denied any involvement in the crime which took place in the nightlife district of Itaewon, close to the US military base in Seoul.He was initially tried in 1997 as an accomplice, while Edward Lee, a Korean-American man who was at the scene, was charged with murder. Both accused the other of killing Jo.Patterson served 18 months in prison for lesser charges including obstruction of justice, while Lee was sentenced to 20 years in jail for murder.In 1998, Patterson was released as part of an amnesty programme, only to find himself a murder suspect again after Lee was acquitted on appeal for lack of evidence.He fled to the United States a year later after investigators failed to renew his travel ban -- a mistake that sparked a storm of criticism.The murder was made into a hit movie in 2009, reviving public anger over the crime and forcing South Korean prosecutors to reopen the case.Patterson was formally charged in absentia with Jo's murder in 2011, and was extradited from the United States in September last year to face trial in Seoul.

His lawyer said he would file another appeal against the verdict.