A D.C. Superior Court jury yesterday found Mark Anthony Watson, 19, guilty of first de w0026 ----- r d BC-06/14/83-SLAY 06-14 0001 NE Man Guilty of Murder In Slaying of Police Officer By Ronald Kessler Washington Post Staff Writer

A D.C. Superior Court jury yesterday found Mark Anthony Watson, 19, guilty of first degree murder in the Sept. 14 slaying of District police officer Donald G. Luning with the officer's own gun. Watson, of Northeast Washington, faces a sentence of 20 years to life in prison.

In a statement at the beginning of the trial a week ago, Assistant U.S. Attorney Harold L. Cushenberry said Luning and his partner had stopped Watson and a passenger because they were in a stolen car. When both fled, Luning--a 10-year police veteran and father of two children--pursued Watson to an apartment where Watson burst in on strangers.

As Luning was about to place handcuffs on him, Watson struggled with Luning and got his gun, Cushenberry told the jury. Watson then pinned the officer to the floor and shot him in the chest, the prosecutor said.

Public defender Stephanie Duncan-Peters told the jury that Watson was afraid of Luning, who was in plain clothes and did not identify himself as an officer when he entered the apartment. "To save himself, he fired the gun," she said.

After deliberating Friday afternoon and again yesterday, the jury found Watson guilty of five of the six charges against him, including premeditated murder and assault on a police officer. Judge George H. Revercomb set sentencing for July 20.