Dennis Benson, a corrections officer who rose through the ranks of Minnesota's penal system and eventually served four years as head of the state's sex-offender treatment program, announced his retirement Tuesday.

He will conclude 38 years with the state on June 5. Nancy Johnston, the program's facility director in St. Peter, will serve as interim director while the Department of Human Services (DHS) seeks a permanent replacement.

On taking charge of the Minnesota Sex Offender Program in 2008, Benson was asked to disentangle it from other DHS services for people with mental illness, developmental disabilities and chemical dependency, and to address constitutional concerns that the sex-offender program had become a place of indefinite detention.

He helped steer the program through the release of Clarence Opheim, an offender who had completed mandatory treatment and was granted a provisional discharge by an appeals panel of the state Supreme Court.

"I am grateful to have been part of two organizations that genuinely care about marginalized populations," Benson said in a statement. "People who want to change can change."

Benson began as a correctional officer, then served as a caseworker, unit director, associate warden and warden of the Department of Corrections' Oak Park Heights and Stillwater facilities. He also served as Department of Corrections deputy commissioner for the Facility Services Division for 12 years.

Staff writer Paul McEnroe contributed to this report. Paul Walsh • 612-673-4482