A 19-year-old Northeast Washington man was sentenced yesterday to life imprisonment for the slaying of D.C. police officer Donald G. Luning, who was shot to death last year after stopping a man to question him about a stolen car.

Mark Anthony Watson of the 1200 block of G Street NE was convicted of first degree murder last month. D.C. Superior Court Judge George H. Revercomb sentenced Watson yesterday to the maximum sentence. Under the sentence Watson will not be eligible for parole for 20 years.

Luning's death Sept. 14 helped spark the current drive to equip all D.C. police officers with bulletproof vests. Luning, 31, who lived in Charles County, died after being shot once in the chest. He was an 11-year veteran of the police force.

At Watson's trial, Assistant U.S. Attorney Harold L. Cushenberry said Luning and his partner stopped Watson and a companion because the officers believed the car the two were in had been stolen.

Watson and his companion fled. Luning, a tactical officer in plain clothes at the time, pursued them to an apartment at 3694 Hayes St. NE. There, according to Cushenberry, Luning attempted to arrest Watson as Watson sat at a table.

"Get up or I'll blow you're head off," Luning told Watson, according to the prosecutor's account. When Watson got up, Luning sheathed his revolver and was about to handcuff the prisoner when Watson grabbed Luning and the two men struggled.

According to Cushenberry, the gun fell out of the officer's holster and Watson grabbed it, pinned the officer to the floor and shot him.

Watson's attorney acknowledged in court that his client had shot Luning. He contended, however, that Watson had done so in self-defense and that Luning had failed to identify himself as a police officer.