Lykken's attorney had argued that because he was age 16 at the time of the alleged crime, the case should start in juvenile court.
He's now 53.
The judge said state law is clear that juvenile court jurisdiction ends once a person reaches age 21, even if the alleged crime happened before the defendant turned 18.
Lykken has pleaded not guilty to an indictment charging six alternate counts of murder in the disappearance of 17-year-olds Cheryl Miller and Pamella Jackson. He's in prison on an unrelated conviction.