U.S District Judge Ralph Erickson also rejected a motion for a new trial for Alfonso Rodriguez Jr., 53, who was convicted last fall of kidnapping resulting in death.
Sjodin, 22, a University of North Dakota student from Pequot Lakes, Minn., disappeared from a Grand Forks shopping mall parking lot in 2003. Her body was found nearly five months later in a Minnesota ravine. Authorities said she had been beaten, raped and stabbed.
Before Sjodin's slaying, Rodriguez had served more than 20 years for offenses that included rape and attempted kidnapping. He got out of prison about six months before the killing.
North Dakota and Minnesota have since toughened their laws against sex offenders, including sentences of life without parole for the most serious offenses and stricter supervision of offenders after they leave prison.
The case also revived debate about whether North Dakota should restore the death penalty. North Dakota's last execution was in 1905. The last person sentenced to death was spared in 1915.
Rodriguez was charged under federal law because Sjodin was taken across state lines.
Rodriguez showed no emotion during the sentencing hearing. He had been offered a chance to speak but declined. His attorney, Richard Ney, gave notice that he plans to appeal.
"The sentence does not reflect the heart of the community," Ney said. "It reflects the fear of the community."
Before the sentencing, about 15 of Sjodin's relatives and friends spoke about her life and the impact of her death. Her mother, Linda Walker, was the last of the group to speak.
"I have been told to talk from my heart," Walker said. "My heart has been torn into a million little pieces."