A Wisconsin woman is suing a psychiatrist for malpractice, claiming he convinced her she had 120 personalities – and then charged her insurance company for group therapy.

Nadean Cool testified yesterday that the US$300,00 (NZ$441,500) treatment by Kenneth Olson left her suicidal and haunted by false memories. The personalities included a duck, the Devil, and angels who talked to God.

"Before I knew it, I was hypnotised," Ms Cool, a former nurse’s aide, testified yesterday. "And when I came out of it, he said ‘I knew it, I knew it. I knew you were a great candidate’."

Dr Olson’s lawyer, David Patton, said the psychiatrist correctly diagnosed multiple personality disorder, and that no malpractice occurred because it was Ms Cool who suggested she was possessed by the Devil.

Dr Olson agonised over her patient’s condition and refused to abandon her, Mr Patton said, who described Ms Cool as a troubled person who had been abused.

Ms Cool and her insurance company, Blue Cross and Blue Shield United, are suing Dr Olson, St Elizabeth Hospital and Legion Insurance. Blue Cross, which paid US$113,000 to Dr Olson and $114,000 to St Elizabeth, said he billed for group sessions, claiming he was counselling more than one person because of her alleged split personalities.

Ms Cool is also suing St Elizabeth’s, where they both worked, claiming it allowed him to perform an exorcism on her and did not monitor the drugs prescribed for her.