Mitchell is believed to suffer from a psychotic illness, according to the testifying forensic psychiatrist, Paul Whitehead.
"Mr. Mitchell was talking with Miss Smart about having babies to the point where Miss Smart actually picked out a name in case that happened," Whitehead testified.
Smart then stood up and left the courtroom.
The testimony was informed by Barzee's recovered journals.
Smart was 14 when she was abducted from her home at knifepoint on June 5, 2002. She was recovered nine months later disguised in wig and sunglasses and walking a suburban Salt Lake City street with Mitchell.
Now 23, Smart has testified that she was forced to enter a polygamous marriage with Mitchell, endured near daily rapes, was forced to use drugs and alcohol, and was taken to California against her will.
The Associated Press contributed to this report.