Lucas County jurors found Robert Bowman, now 75, guilty Friday of killing 14-year-old Eileen Adams. Judge Gene Zmuda handed down the sentence.
Adams disappeared on her way home from school in Toledo. Her body was found weeks later wrapped in a rug in a southern Michigan field.
Police didn't connect Bowman with the killing until the early 1980s when his former wife said she had seen the girl tied up in their basement. It wasn't enough to bring charges.
Bowman was charged five years ago when police say DNA linked him to the killing.
Bowman says he will appeal.