Despite the drastically lengthened sentence of 65 years, Smith grinned and guffawed as the judgement was read.
Later he flashed a broad smile as he was led from the courtroom, said C.J. Robinson, chief assistant district attorney.
"I don't think Mr Smith will be smiling long when he gets to prison," Robinson told USA Today.
"We are very pleased with this sentence. Because the sentences are consecutive, it will be a long time before he comes up for even the possibility for parole, at least 20 to 25 years," he added.
Smith was tried under Alabama's accomplice laws and was found responsible for the acts that led to the death of a A'Donte Washington, 16, of Montgomery.
Alabama's accomplice law states a person is legally liable for the behavior of another who commits a criminal offense if that person aids or abets the first in committing the offense.
Smith did not kill Washington, who he had taken part in thefts with, but was found responsible for his death.
Members of the group, including Washington, fired shots at Millbrook police officers who responded to a call of a burglary in February 2015.
When Washington, armed with a .38 caliber revolver, ran towards one attending officer, pointing a .38 caliber revolver in his direction, the officer fired his police-issued sidearm four times, killing the boy.
An Elmore County grand jury cleared the officer of murder and declined to release his name.
The fault for Washington's death fell in part on Smith, the court found.
"The officer shot A'donte, not Lakeith Smith," Smith's lawyer, Jennifer Holton, said.
"Lakeith was a 15-year-old child, scared to death. He did not participate in the act that caused the death of A'donte. He never shot anybody."
Jadarien Hardy, 22, Jhavarske Jackson, 23, and La'Anthony Washington, 22, all pleaded guilty of felony murder, burglary and theft, court records show.
They await sentencing.
