Mauldin is charged with felony injury to a child and faces up to life in prison if convicted. He has pleaded not guilty by reason of insanity, which the state defines as a severe mental illness that prevents someone who is committing a crime from knowing that it is wrong.
Michael Fuller, an associate clinical professor at the University of Texas Medical Branch at Galveston, testified that Mauldin's medical records indicate he has been previously diagnosed with major depressive disorder, bipolar disorder and schizophrenia and has claimed to hear voices.
The records also indicate Mauldin has suffered head injuries at least three times in his life, including being thrown against a couch by his father when he was in elementary school, that he wasn't taking his medication, the anti-depressant Zoloft, and that he suffered from low blood sugar.
"I believe that it is possible, possible that at the time of this event, one or more of these additional variables was affecting his awareness, that rendered him to be impaired of his judgment," Fuller said when questioned by defense attorney Sam Cammack III.
But when asked by prosecutor Xochitl Vandiver if Mauldin was insane at the time he is accused of hurting his daughter, Fuller said, "I was unable to find sufficient evidence to suggest that Joshua Mauldin met the criteria for insanity at the time of the offense."
Fuller later said his report evaluating Mauldin suggested some ambiguity on the issue of insanity and whether he knew the difference between right and wrong.
During Fuller's testimony, Cammack used Mauldin's medical records to try to show his client was mentally ill and not responsible for his actions. Cammack has told jurors that Mauldin started hallucinating just before hurting his daughter.
Fuller testified Mauldin has claimed to be suicidal and that his family had a history of schizophrenia.
Since Mauldin has been in jail, he has been given anti-psychotic drugs and the anti-depressant Prozac and his audio hallucinations have greatly lessened, Fuller said.
"He appears to be doing well," Fuller said.
But Vandiver used the same medical records to suggest that Mauldin has repeatedly made claims since he was a boy of hearing voices and suffering mental illness as a way of getting out of trouble.
When asked by Vandiver, Fuller told jurors that he believed the head injuries Mauldin had suffered were not severe enough to affect his mental state, that Galveston County records indicate Mauldin lied about being suicidal in order to be transferred to another cell and that claims Mauldin has heard voices since he was 10 years old or that there is a family history of schizophrenia are not supported by records.
"All of it could be lying?" Vandiver asked.
"I suggested that is a possibility," Fuller said, later adding he believed Mauldin's claims of hearing voices.
Fuller also testified he has seen no evidence where he could diagnose Mauldin with suffering from schizophrenia, bipolar disorder or mania. He did diagnosis Mauldin with several other disorders, including major depressive disorder and anti-social personality disorder.
Testimony was expected to continue on Thursday.
On Tuesday, prosecutors rested their case after four days of testimony.
Investigators testified Mauldin at first told them the infant had been sunburned as he and his family had moved from his hometown of Warren, Ark., to Galveston, located about 50 miles southeast of Houston, so he could be a preacher.
Mauldin later told investigators that Ana was injured after he tripped and spilled hot water on her.
In a videotaped statement he gave to police and that was shown to jurors, Mauldin used a Teddy bear to demonstrate how he put his daughter in the microwave.
Mauldin is also accused of punching the baby and putting her in a refrigerator and a hotel-room safe.
Ana suffered second- and third-degree burns to her left ear, cheek, hand and shoulder and required two skin grafts. Part of her left ear had to be amputated.
Officials say Ana, whose first birthday was earlier this month, is still receiving treatment but is doing well and living with relatives in Texas.