The D.C. Court of Appeals on Thursday overturned the 2010 conviction of a District man who was charged with fatally stabbing a man during a fistfight outside a Northwest Washington carryout.

The three-judge panel ruled that the judge overseeing the case, Gerald I. Fisher, erred in one of the instructions he gave jurors before they began deliberations.

In October 2010, a jury convicted Adrian Lee, 37, of voluntary manslaughter and carrying a deadly weapon in connection with the killing of Chiagbanwe Ukaoma, 22. Defense attorneys argued that Lee had acted in self-defense. A year later, Lee was sentenced to 13 years in prison.

During the trial, prosecutors argued that Ukaoma and several of his relatives were purchasing food at the Howard China carryout in the 2800 block of Georgia Avenue NW on Feb. 25, 2009, when they encountered Lee and his friends.

Outside the carryout, according to court documents, one of Lee’s friends got into a fight with Ukaoma’s brother, and both groups got into a physical altercation. During the melee, prosecutors said, Lee pulled out a pocketknife and stabbed Ukaoma, puncturing his heart. Lee’s public defenders argued that their client acted in self-defense and to protect his friend, Donald Branch, who was being beaten.

During the trial, Branch testified that although he was on the ground, being beaten by four men and bleeding from his mouth and nose, he never thought that he was in grave danger and believed that he had the fight under control.

Lee approached the fight and pulled out a pocketknife to scare the men away from Branch. While waving the knife, Lee was hit in the head with a fist. Lee then began swinging the knife with his right hand, stabbing Ukaoma in the chest.

When it came time for deliberations, Fisher instructed the jurors to consider Branch’s belief that he thought he was never in actual danger.

In their 16-page decision, the appellate judges ruled that Fisher’s instruction was “erroneous” and “prejudicial” against Lee. The judge, the court said, should not have instructed the jury that Lee’s right to defend his friend depended on Branch's beliefs, because it was Lee’s state of mind that mattered. As a result, the judges unanimously reversed the conviction and ordered a new trial.

A spokesman for the U.S. attorney’s office said prosecutors were “reviewing” the opinion and declined to comment further.