A man who pleaded guilty to sexually assaulting three women and trying to rape a fourth apologized to his victims this morning and asked a Jefferson County district judge to lock him away for life.

Judge Philip J. McNulty, obliged, sentencing Marc O’Leary to 327 — and a half — years in prison.

O’Leary, 33, of Lakewood stalked his victims, broke into their homes while they were sleeping and raped them for hours before forcing them to shower and brush their teeth to get rid of any evidence.

He also took photos during several of the attacks — images that police later found during a search of O’Leary’s home.

DNA found on several victims also matched O’Leary or one of his family members, detectives had said.

O’Leary pleaded guilty in October to 28 counts, including sex assaults of women in Golden, Westminster and Aurora and an attempted assault in Lakewood.

He also is charged with two sex assaults in Washington state, where he lived before moving back to Colorado in 2009.

As some of his victims addressed the court this morning, O’Leary rocked back in forth in his chair but otherwise showed no emotion. His sister put her fingers in her ears as her brother’s crimes and their impact were detailed.

Then, O’Leary spoke. For 45 minutes he explained that he had been living a double life, and that his sexually deviant thoughts began when he was just 5.

“I’m standing here because I need to be in prison,” O’Leary said. “I know that probably more than anyone in this room. I’ve known it for awhile.”

Chief Deputy District Attorney Robert Weiner has called the case “one of the most extreme cases we have seen.”

He said prosecutors agreed to a plea deal because the agreement almost guarantees O’Leary will spend the rest of his life in prison, and the deal would save the victims the trauma of a trial.

O’Leary is also expected to plead guilty in Washington. He will likely serve his prison time in the Colorado Department of Corrections.

The sentencing hearing is scheduled to begin at 8:30 a.m. before District Court Judge Philip McNulty.

Sara Burnett: 303-954-1661 or sburnett@denverpost.com