A key expert witness testified Friday that serial rapist Thomas Duvall is not ready for release from Minnesota’s sex offender program, arguing that he remains fixated on deviant and violent sexual thoughts despite decades in treatment.

“He is a man obsessed with sex — most of it violent,” said Dr. James Alsdurf, who described Duvall as a sexual sadist. He added, “If you’re Tom Duvall, sex is always there. It’s an enormous pressure.”

Alsdurf is a forensic psychologist appointed by a state Supreme Court appeals panel reviewing Duvall’s petition for conditional release into the community. He said he reached his conclusion after giving Duvall a series of psychosexual exams and reviewing more than 10,000 pages of Duvall’s criminal and treatment records, which include details of his brutal rapes of teenage girls in the 1970s and 1980s.

For the third straight day, much of the testimony centered on Duvall’s personal journals, or “fantasy logs,” maintained as part of his therapy. In the logs, which span more than 500 pages, Duvall described fantasies involving teenage girls, female body parts and past victims, according to testimony. The journals have become a central piece of evidence in the state’s case against his release.

The inclusion of the journals in this week’s hearing has been controversial because Duvall was encouraged to write them as part of his therapy. Some treatment professionals have warned that their use in a public trial could have a chilling effect on other offenders, making them less likely to reveal their thoughts honestly in therapy.

Alsdurf said the personal journals are significant because they demonstrate that Duvall is still preoccupied with deviant sexual thoughts, many of them “dominant and controlling.” In some entries, for example, he used objectifying language to describe female body parts.

“They represent what’s in Tom Duvall’s head,” Alsdurf said. “He is what I would describe as ‘hypersexual.’ He is constantly aware of and focused on sexual topics.”

The focus on Duvall’s inner thoughts also seemed to perplex members of the three-judge Supreme Court panel hearing his petition, and set off a broader discussion about the purpose of sex offender therapy. At Friday’s hearing, one of the judges questioned whether it was “a realistic goal” for offenders to “not think about sex,” while questioning how a treatment regime could address a person’s thoughts.

In his 17 years of confinement at the Minnesota Sex Offender Program (MSOP), Duvall has not actually acted out on his violent and deviant thoughts — a fact that his attorney has repeatedly stressed in court.

Duvall has gone on more than 100 supervised outings, volunteers at a thrift shop three times a week, and regularly attends a support group in Minneapolis — all without a single incident of violent or disruptive behavior, MSOP staff said in testimony. In addition, Duvall’s treatment team supports his petition for discharge into the community, as does Dr. Lauren Herbert, the director of forensic evaluation at the Minnesota Department of Human Services.

Still, the testimony of Alsdurf, coming toward the end of the five-day hearing, casts fresh doubt on whether Duvall is ready to be released from the MSOP, where he has been confined since 1991. Duvall has a total of seven convictions for criminal sexual assaults, including one for a particularly brutal attack in 1987 in which he raped a woman while hitting her with a hammer.

Although Duvall has been candid about his crimes in testimony, and MSOP officials testified earlier this week that he has made great progress in therapy, his petition for release has been complicated by his own admissions that he continues to have deviant sexual fantasies. He has also shown deceptive responses in five of his last six polygraph tests when asked about his deviant sexual fantasies. This includes a failed polygraph exam taken just last month.

“It’s so pervasive. It’s like a disease that he’s had over time that he can’t control,” Alsdurf said in testimony. “He’s like the person who is trying to stop smoking but all he can think about all day is smoking.”