A group of Minnesota sex offenders has asked the U.S. Supreme Court to examine whether the state is violating the Constitution by confining people indefinitely in prisonlike treatment centers after they have already completed their criminal sentences.

In a petition filed Friday, attorneys representing the offenders allege that the Minnesota Sex Offender Program (MSOP) infringes on their fundamental due process rights by operating a program without the basic safeguards of the criminal justice system — effectively turning the MSOP into a "life sentence." Offenders, the petition argues, lack timely access to the courts and the opportunity for regular reviews to determine whether they still pose a danger to the public or deserve to be released.

"The fatal flaw of Minnesota's civil commitment scheme … is its failure — by statute or implementation — to meaningfully ensure on a regular, periodic basis that people committed to the MSOP continue to satisfy the standards of commitment," attorney Dan Gustafson wrote in the petition filed with the Supreme Court.

After a six-week trial in 2015, U.S. District Judge Donovan Frank declared the program unconstitutional, in large part because of the program's absence of regular risk assessments of offenders. Most of the 20 states with civil commitment laws, including Wisconsin and New York, require annual or biannual risk assessments and court hearings to determine whether offenders still meet the criteria for confinement.

"Hundreds of civilly committed people in Minnesota have never received a risk assessment and hundreds more have risk assessments that are outdated and therefore invalid," Gustafson's petition said.

The Eighth Circuit Court of Appeals in St. Louis reversed Frank's ruling in January, setting the stage for an appeal to the nation's highest court.

Minnesota now confines more sex offenders per capita than any other state and has the lowest rate of release. About 720 offenders are now detained at secure treatment centers in Moose Lake and St. Peter.

Only one offender has been fully released without conditions from the MSOP since the program was established in 1994, and that occurred only last year.

The Supreme Court hears only about 75 cases a year, a tiny fraction of the thousands of cases that are brought before it each year.

Chris Serres • 612-673-4308

Twitter: @chrisserres