The man charged in the kidnapping of Utah teenager Elizabeth Smart (search) was declared mentally incompetent to stand trial Tuesday.

The decision by Judge Judith Atherton (search) will send Brian David Mitchell (search) to a state hospital until he is deemed capable of standing trial.

Atherton issued her decision after six days of hearings over the past seven months. Mitchell repeatedly shouted Biblical admonitions and sang hymns during the hearings, prompting him to be removed from court several times.

The judge's decision covered the sweep of Mitchell's life in a family that testimony showed had a history of mental disorder. Mitchell was the third of six children and a "loner" in a "highly dysfunctional" family, the judge wrote.

"It is the court's conclusion that that the preoccupation, distress and impaired social functioning exhibited by the defendant are symptoms of a delusional disorder," Atherton wrote.

The judge dismissed the prosecution argument that Mitchell was a narcissist with an extreme set of religious beliefs. She found that his beliefs were based on psychotic delusions and that he was incapable of making rational decisions or assisting in his defense.

Under Utah law, Mitchell will be back in court after three months for proceedings to determine whether his mental state has changed, prosecutor Bob Stott said.

"We're disappointed but we respect the judge's decision. She's given a lot of time and energy to the matter, and we'll follow the decision," Stott said. "Criminal charges are still pending. It just means we can't go forward until he regains his competency."

Mitchell, 51, is accused of kidnapping then 14-year-old Elizabeth from her bedroom in 2002, sexually assaulting her and keeping her as his second wife.

Mitchell and wife Wanda Barzee, 59, were charged with kidnapping, aggravated sexual assault, aggravated burglary and attempted aggravated kidnapping. Barzee was found incompetent to stand trial last year.

Mitchell also is charged in the attempted abduction of Elizabeth's cousin.