North Dakota ? A rapist who killed college student Dru Sjodin six months after being released from prison was formally sentenced to death Thursday in a case that led to tougher sex-offender laws.

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 in 2003 from a Grand Forks shopping mall parking lot. 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 was released from prison about six months before the killing.

Rodriguez was charged under federal law because Sjodin was taken across state lines. Barring a successful appeal, Rodriguez will die by injection at a federal prison in Terre Haute, Ind.