CENTENNIAL, Colo. » The mental health professional with the most access to James Holmes’ mind before he carried out his deadly attack on a Colorado movie theater is expected to testify in his death penalty trial on Tuesday.

Dr. Lynne Fenton saw Holmes five times in 2012 while he was a neuroscience graduate student at the University of Colorado. She prescribed him medication for depression and anxiety, concerned that he had a social phobia after he confessed thoughts of killing people, according to testimony from other witnesses.

Her testimony is among the most highly anticipated, as Fenton has never spoken publicly about their sessions. She remains bound by the trial judge’s gag order, and a civil suit says she should have done more to stop Holmes. But Holmes waived his patient-client privilege when he pleaded not guilty by reason of insanity, opening the door for her to take the stand.

Holmes is charged with killing 12 people, wounding 58 with gunfire and leaving 12 others injured in the attack on July 20, 2012. Questions remain about whether anyone could have stopped him.

Holmes said he pointedly kept Fenton uninformed as he plotted his attack. He never told her about the arsenal of weapons he was assembling. His elaborate schemes and to-do lists were kept in a journal that he didn’t send to her until hours before his assault, and it lingered in a campus mailroom for days thereafter.

His list for their sessions included: "Prevent building false sense of rapport … deflect incriminating questions … can’t tell the mind rapists plan."

But he did tell her and two other therapists at the university that he was having thoughts of killing people. Prosecutors said Fenton didn’t believe Holmes would act, as other patients sometimes mention similar thoughts.

But Fenton did contact a campus-wide threat assessment team in June 2012, more than a month before the attack and told a campus police officer about her concerns after Holmes sent her a threatening email. Fenton, however, rejected the officer’s offer to arrest Holmes and place him on a 72-hour psychiatric hold, according to the civil suit.

In interviews with a court-appointed doctor two years after the shooting, Holmes said he kept Fenton at bay. He didn’t go out of his way to build rapport, seeing their relationship as artificial, he said.

"I kind of regret that she didn’t lock me up so that everything could have been avoided," Holmes told William Reid, a state psychiatrist appointed to determine whether he was legally sane.