A U.S. citizen who received a 20-year jail term last week for murdering a South Korean student in 1997 has filed an appeal with a higher court, legal sources said Monday.

Arthur Patterson, who has been convicted of stabbing then-college student Cho Joong-pil multiple times at a Burger King in the popular foreigner district of Itaewon in central Seoul, brought the case to the Seoul High Court.

Last week, the Seoul Central District Court handed down a jail term 19 years after the incident took place.

The 36-year-old has been denying the charges and pointing to Korean-American Edward Lee, who he was with at the time of the homicide, as the culprit.

The court acknowledged Lee as an accomplice but did not punish him due to double jeopardy.

A local court found Lee guilty of murder and sentenced him to life in prison in 1998, but he was acquitted by the Supreme Court the following year due to a lack of evidence.

At the time, Patterson, of half-Korean parentage, was in Seoul as the dependent of a civilian worker with the U.S. military. He fled the country in 1999 after he was pardoned and released on charges of destruction of evidence and weapon possession.

His departure was possible because law enforcement authorities failed to extend his foreign travel ban.

Legal sources say the appeals trial will mainly cover the legitimacy of evidence that was accepted by the justice department and possible errors in applying legal principles. 

Patterson was indicted for murder in December 2011 and was extradited to South Korea in September 2015. (Yonhap)