CHICAGO (CBS) — A Chicago man who is a registered sex offender has been ruled a sexually violent person.

A jury found that David Lewis, 50, is a sexually violent person and Cook County Circuit Court Judge Peggy Chiampas ruled that he must remain in custody of the Illinois Department of Human Services for treatment, according to a statement from the Illinois attorney general’s office. He was returned to the Sexually Violent Person Treatment and Detention Facility in Rushville, Illinois.

“I appreciate the jury’s recognition that this offender’s history of sexual violence means he should not be allowed to reenter society,” Attorney General Lisa Madigan said in the statement.

David Lewis (Source: Illinois Department of Corrections)

Lewis had a history of indecency and exposure to women and girls in the 1980s when he was arrested in 1992 for an armed robbery, the attorney general’s office said. He planned to sexually assault the victim before she was able to escape the robbery. While on bond for that incident, Lewis was charged with two aggravated criminal sexual assaults at knifepoint.

He was 25 at the time, and at least one of the victims was younger than 18, according to the Illinois Sex Offender Registry.

Lewis was found guilty in all three cases and sentenced to 45 years in prison for the aggravated sexual assaults and nine years in prison for the armed robbery, to run concurrently, prosecutors said.

To be committed under the Sexually Violent Persons Commitment Act, “a person must have been convicted of a sexually violent offense and suffer from a mental disorder,” the statement said. “Prosecutors must also prove that the offender is likely to commit future acts of sexual violence if released from custody. Once committed to IDHS, offenders are re-evaluated on a regular basis to determine if they continue to meet the criteria for commitment as a sexually violent person.”

(Source: Sun-Times Media Wire © Chicago Sun-Times 2017. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)