But the prosecution in their closing arguments claimed the Mitchell is faking mental illness.
"He's a predatory chameleon with the cunning to adapt his behavior to serve his needs and desires at any given moment," Assistant U.S. Attorney Diana Hagen told the jury.
The trial spanned five grueling weeks, during which Smart took the stand to describe in frank language what happened during her nine-month captivity.
During the three days Smart spent on the stand last month, she gave excruciating personal testimony that painted Mitchell as a cruel religious zealot obsessed with sex.
Speaking in a controlled voice, her words tinged with anger, Smart called Mitchell selfish and a "hypocrite" who raped her at every chance he got even while proclaiming himself to be God's servant.
Smart, now 23, told the jury that Mitchell talked to her during her captivity about what would happen if police found them.
"He knew he would go to prison. But then he also said that I ... and the other wives ... would come and testify in his behalf," Smart testified. "And he said that he would be released and he would be killed and lie dead in the street for three days and then he would be resurrected and he would go on to fight the Anti-Christ."
She also spoke of being forced to drink alcohol and smoke marijuana, which disgusted her.
Smart was 14 when she was kidnapped from her bed in Utah. She has said she was forced to "marry" Mitchell in an impromptu ceremony shortly after the kidnapping and that he would often beg her for sex, angering his accomplice Wanda Barzee, who was jealous of the attention Mitchell gave Smart.
Remaining poised throughout her testimony, Smart detailed her nightmarish nine months with Mitchell and Barzee. She said that at one point she was confronted by a police officer looking for Elizabeth Smart and he wanted to look under the veil Mitchell made her wear. She said she was so afraid of Mitchell's death threats that she didn't speak up and was heartsick that the officer wasn't more persistent.
The officer, Det. Ron Richey, has said he was devastated to learn later that he had been looking right at Smart and didn't do more to help her.
When she was finally rescued, she initially denied her identity out of fear that Mitchell would make good on his death threats.
Barzee pleaded guilty to federal kidnapping charges last year and was later sentenced to 15 years in prison.
At one point in the trial, Smart stormed out of the courtroom after a psychiatrist testified that she had baby names picked out in case she became pregnant by the man who held her captive.
Psychiatrist Paul Whitehead told the court that Smart had been "chastised" by Mitchell and Barzee, according to The Associated Press.
"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.
As Whitehead described Smart choosing a baby name, Smart left her front row seat in the courtroom and went to a private area. Her mother quickly followed.
Mitchell has been removed from the courthouse nearly every day for refusing to stop singing hymns, and one time was removed and the trial temporarily halted after he to appeared have suffered a seizure, collapsing in court.