Brian David Mitchell is charged with kidnapping and unlawful transportation of a minor across state lines for the purposes of illegal sexual activity.
The trial is heading into its fourth week, and the defense called on psychiatric evaluators to testify about Mitchell's competency.
A therapist from a hospital where Mitchell was incarcerated from 2005 to 2008 testified on Monday. Gregory Porter told jurors that he was skeptical about whether Mitchell was mentally ill when he was first admitted in 2003.
Porter said he later diagnosed Mitchell as delusional, particularly about religion.
Prosecutors argue that Mitchell is faking mental illness to avoid prosecution.
Smart has testified that she was forced to enter a polygamous marriage with Mitchell, endured near daily rapes and was forced to use drugs and alcohol.
If convicted, Mitchell could spend the rest of his life in prison.