Otto Emil Koloto, 23, was convicted in March of first-degree murder for the July 13, 2008, slaying of Lacy, a South San Francisco resident, who was shot in the head near City Hall.
Prosecutors said Koloto had ordered Lacy at gunpoint to give him his gold chain, which bore a diamond-encrusted cross. When Lacy refused and instead lunged at him, Koloto shot him in the head, according to prosecutors.
Koloto's explanation that the chain had snagged on his sweatshirt when Lacy lunged at him, accidentally causing the gun to fire, was implausible, prosecutors argued.
Before the sentence was announced, Lacy's brother, William Lacy, addressed Judge Kenneth Shapero and Koloto, who was dressed in a red prison jumpsuit.
Lacy said he realizes Koloto may not have intended to kill his brother that night, but said Koloto's testimony in court had slandered his brother's name.
"Before my brother died, Koloto told him to 'give me your chain, bitch.' Well now you can go and die in prison, bitch."
Lacy's stepbrother, Alex, his stepbrother's wife, and three of Lacy's friends sobbed quietly in the audience during William Lacy's comments.
Shapero also addressed Koloto.
"You made choices and decisions of using a loaded gun that led to a tragic loss," Shapero said. "It's senseless, there's no reason for it. But there has to be accountability."
Koloto's attorney Andy Gutierrez said he plans to file an appeal.
"It's just a sad, sad day," Gutierrez said. "It's obviously a tragic loss to the family. They've suffered an immeasurable loss. I think if he were to go back in time and change some things that night, I'm sure he would."