Twenty-nine-year-old Payne was sentenced on Monday.
Payne had testified he thought he was being robbed and did not know that the people outside the door of his apartment were police, looking for another man inside the unit.
But the jury found he did not act with sudden passion, a finding that could have resulted in a sentence of two to 20 years.
Smith, who was 43, was killed almost instantly when Payne fired through the door, striking him near his left eye.
