A man accused of shooting a sheriff's officer was convicted Wednesday and faces a mandatory 20-year prison sentence.

Because of a prior drug-trafficking conviction and because the new conviction is aggravated assault on a police officer, Cory Lee will have to serve the maximum sentence, Assistant District Attorney Geoffrey Fogus said.

Mr. Lee, 36, shot Richmond County sheriff's Sgt. Elijah Parker in the early morning hours of Dec. 26.

Sgt. Parker was working a second job, security work at the Soundtrack Supper Club on Laney-Walker Boulevard, when he was shot in the chest by a 9 mm handgun. Sgt. Parker was in full uniform, including the bullet-proof vest that saved his life.

Mr. Lee, according to testimony, might have been targeting another man in the parking lot when he shot Sgt. Parker.

Settling disputes with guns was Mr. Lee's modus operandi, Mr. Fogus told the jury in his closing argument. In 1996, he was arrested on but not convicted of shooting Tyrone Jones, who is also a convicted drug dealer.

Defense attorney Charles Lyons tried to convince the jury the state's case lacked certainty.

"Nobody likes to hear of a police officer getting shot," Mr. Lyons said in closing arguments.

But he asked the jury to focus on inconsistencies in testimony, and the investigators' inability to find a gun on Mr. Lee or any gunshot residue on his hands.

Mr. Lee, who has been in custody since his arrest the night of the shooting, will be sentenced by Judge James G. Blanchard Jr. A sentencing date hasn't been set.