A DeKalb County jury Thursday found Neuman guilty but mentally ill in the shooting and also found him guilty of possession of a firearm during the commission of a felony, The Atlanta Journal-Constitution reported.
Neuman has said he was visited by a demon and angel who looked like Barry White and Olivia Newton-John.
In announcing the sentence, DeKalb County Superior Court Judge Gregory Adams called the shooting a "planned execution," the newspaper said.
Neuman's attorneys said they will appeal.
Neuman had pleaded not guilty by reason of insanity in the Nov. 18, 2010, slaying of Russell "Rusty" Sneiderman, 36, who was gunned down in November as he dropped his son off at preschool. Neuman was Andrea Sneiderman's onetime boss at GE Energy.
Andrea Sneiderman's attorneys released a statement saying: "Andrea is grateful for and relieved by the jury's guilty verdict and the sentence. Nothing can bring back her husband, but it is reassuring to her that, after all of the noise and distractions surrounding this case, some measure of justice has been done for Rusty.
"Rusty's family misses and mourns him every single day. But today, at least, the family can be comforted by the fact that his killer will spend the rest of his days behind bars."