The jury on Monday convicted 28-year-old Jquante Crews, and a judge sentenced him to life in prison without parole plus 10 years. Forrest was fatally shot in July 2009.
Prosecutors say Forrest was robbed at gunpoint by Demario Ware, who has already been convicted in the case. Prosecutors say Ware fled with Forrest's championship ring and Rolex watch. As he chased Ware,Forrest encountered Charmon Sinkfield, the alleged gunman.
Prosecutors say Crews drove the getaway car.
Ware was convicted in August on felony murder and armed robbery charges and was also sentenced to life without the possibility of parole.
Prosecutors are seeking the death penalty against Sinkfield.