By JIM SALTER
ST. LOUIS (AP) — A hearing has begun that will decide whether to overturn the conviction of a Missouri man who has spent nearly three decades in prison for a murder that two other people have since confessed to committing. St. Louis Circuit Attorney Kim Gardner is backing Lamar Johnson in his effort to vacate his conviction. But the Missouri attorney general’s office says Johnson was rightfully convicted and should remain in prison. The hearing is expected to last all week. Johnson was convicted in 1995 of killing Marcus Boyd over a $40 drug debt and received a life sentence. James Howard, who is serving a life sentence for an unrelated murder, testified Monday that he and another man killed Boyd.