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In unusually explicit testimony Thursday, serial rapist Thomas Duvall opened up about his long and violent past, admitting that he still has sexual fantasies about teenage girls that he assaulted more than three decades ago.

At the same time, Duvall, 61, displayed bursts of emotion and remorse in the courtroom, insisting that he is capable of managing his sexual impulses after years in treatment and is prepared to move into a supervised home in the community.

"I have paved my own road to where I am today," said Duvall, occasionally wiping away tears. "I have no more excuses in life."

Duvall's testimony shed new light on the extremely brutal nature of his past crimes, while providing a view of the steep challenges that sex offenders face when they seek even supervised release from Minnesota's sex offender program. In this case, Duvall's candidness in therapy has been used as ammunition against him during a contentious, four-day trial before a state Supreme Court appeals panel considering his petition for release.

Duvall's case also underscores lingering questions about whether a sex offender's thoughts and fantasies, which are sporadic and difficult to interpret, should be the subject of a court trial. Offenders are less likely to be honest about their deviant impulses or mental health problems if they believe such information will later be used to keep them confined, treatment professionals warn.

Attorneys for the state and Hennepin County, which oppose Duvall's petition for provisional discharge, have seized on the content of Duvall's personal journals, or "fantasy logs" — which he was encouraged to maintain as part of his treatment at the Minnesota Sex Offender Program (MSOP) — as evidence that he retains violent impulses and remains a risk to the public.

The logs contain more than 500 pages of Duvall's inner thoughts, stretching from 2014 to 2017, in which he describes sexual fantasies about teenage girls, female body parts, and past victims. The logs also show that Duvall has continued to masturbate to "deviant themes," a state administrator testified Thursday.

The trial marks the second time that Duvall's personal journals have been used against him in court, and it highlights a paradox of Minnesota's program for civil commitment of sex offenders who have completed their prison terms. On the one hand, offenders are encouraged to be honest about their sexual thoughts as part of their treatment, and cannot progress through the MSOP without such transparency. But such information can be used against them in court if they petition for release.

"This is just one more example of the convoluted nature of Minnesota's program, and why it's almost impossible to get out" of the MSOP, said Warren Maas, president of the Minnesota Association for the Treatment of Sexual Abusers, in an interview.

'Euphoric' memories

In sometimes halting testimony, Duvall admitted that he still experiences what therapists call "euphoric recall" when he visualizes past victims, including a 17-year-old girl he sexually assaulted at the Minnesota State Fairgrounds in 1977. "Sometimes when I'm masturbating, the thought of a past victim will flash in my head," Duvall said during cross-examination Thursday. "I get euphoric recall from my past crimes."

Duvall also recounted details of several of his more horrific crimes, which stretch back to the 1970s. On Dec. 26, 1987, he knocked on the door of a 17-year-old girl's apartment in Brooklyn Park and asked to use the telephone. He then bound the girl with an electrical cord and raped her over several hours while hitting her with the handle of a hammer.

Asked in court why he used the hammer, Duvall responded matter-of-factly, "Because she was making noise and I wanted her to stop."

Duvall also admitted to an earlier incident, in which he lured two teenage girls to his home with promises of alcohol and drugs and then used a shotgun to force them into oral sex. In testimony, Duvall acknowledged that he was sexually aroused by the girls' fear. "I got a terrible and horrendous background," he said.

While contrite through most of his two-hour testimony, Duvall took issue with the use of the personal journals, calling it "unfair" that people were making judgments based on his entries. Duvall also said that he has been locked up for so many years that his sexual thoughts invariably date back to the "unhealthy and deviant" relationships for which he was locked up in the first place. Duvall has been civilly committed to the MSOP since 1991.

Polygraph tests

Duvall said he takes medication to manage his sexual arousal, and has a network of therapists and relatives who will support him in the community. "You know, one of the biggest thoughts in my past used to be, 'Who cares?' " he said, wiping his eyes with the back of his hand. "But I have so many people today who care."

Lawyers have challenged Duvall's honesty with treatment professionals, pointing out that he has registered a "deception" signal on five of six polygraph exams since 2014. As recently as March 13, Duvall failed a polygraph test in which he was asked about masturbating to deviant sexual thoughts.

"Would you agree that it continues to be a concern that he cannot pass a polygraph?" Assistant Hennepin County Attorney Theresa Couri asked during cross-examination of a state official Thursday.

In recent years the state has been under increased pressure, from the federal courts and a lawsuit, to demonstrate that it operates an actual treatment program with measurable results, and not facilities designed to punish and detain offenders indefinitely. Over the past two years, the program has approved about a dozen offenders for conditional release into the community, compared with just three in the program's previous 20-year history.

Chris Serres • 612-673-4308 Twitter: @chrisserres