Dr. Henry Carlisle is the therapist of Janis Donovan, who presented symptoms of dissociative identity disorder. He was horrified Janis was becoming more unstable from her condition, only previously providing her counseling. Assisting the office in getting to Janis once she was tracked, despite the team's objections about his expertise and understanding, Carlisle directed Janis' session of hypnosis to figure out her mental state and find out if she was guilty of crimes she accused herself of in her alter personalities.
Janis before had falsely alleged she abused her baby niece, then had hit Stabler. During the session, she threw a chair at Dr. Carlisle, before she came back to her present-minded self. Despite her demonstrations of violence and endangerment, Carlisle was delighted that her condition was diagnosed and insisted she return home so she'd start outpatient treatment to recover from an overwhelming day.
Janis later killed the parents of her and her sister, Cass Magnall, and took Stabler's wife Kathy hostage with a large kitchen knife. But at the trial, she had an episode and was committed to inpatient mental healthcare when found not guilty by insanity. It was revealed Janis faked the condition to get off on the murders, with Cass planning the whole thing with her too, from the fake episodes to the murders. Cass was arrested when her role was found out because she was culpable of conspiracy. (SVU: "Alternate")