A group of Minnesota sex offenders are appealing a federal court ruling in early January that upheld the constitutionality of the state's sex offender program.

In a petition filed Tuesday, attorneys representing the offenders argue that a three-judge panel of the Eighth U.S. Circuit Court of Appeals in St. Louis erred when it overturned a 2015 court ruling out of Minnesota. The Minnesota judge had found that the state's sex offender program violated civil liberties by locking people up indefinitely without regular review.

The attorneys are seeking a rehearing before the full Eighth Circuit Court of Appeals.

After a six-week trial in 2015, U.S. District Court Judge Donovan Frank in St. Paul declared the Minnesota Sex Offender Program, or MSOP, unconstitutional, citing its low rate of release and the state's failure to conduct regular risk assessments of the roughly 720 offenders confined indefinitely at secure treatment centers in Moose Lake and St. Peter.

The judge ordered the state to make sweeping reforms, including the development of less-restrictive treatment in the community.

However, the three-judge panel in St. Louis ruled that the sex offenders had failed to prove the state's actions "shock the conscience" and violated their fundamental liberties. The ruling has derailed efforts at reform by removing any immediate court pressure to put offenders on a clearer path toward release.

Minnesota has more civil commitments of sex offenders per capita than any state in the nation, spending an average of $124,000 per detainee per year.

Dan Gustafson, lead attorney for the class of offenders, said the appellate panel applied an improper standard ("shock the conscience") that placed too high a burden on the sex offenders to demonstrate a violation of their due process rights.

The basic facts supporting the sex offenders' claims were undisputed during the trial, he added. Among these, he said, is that Minnesota does not perform regular, periodic risk assessments to determine if detainees still meet the statutory criteria for confinement.

"There is no dispute that there are hundreds of individuals confined at MSOP that the state of Minnesota doesn't even know if they continue to satisfy the constitutional criteria for commitment," Gustafson said. "That was not disputed."

If the Eighth Circuit declines to rehear the case, Gustafson said he intends to appeal to the U.S. Supreme Court.

In a statement, state Human Services Commissioner Emily Piper, whose agency oversees the MSOP, said the state and her agency "will continue to defend the position that the Minnesota Sex Offender Program is constitutional and necessary to ensure public safety, as the Eighth Circuit previously ruled."

Chris Serres • 612-673-4308

Twitter: @chrisserres