HOUSTON -

The Houston mother accused of burying her baby alive headed back to court Wednesday for day six in her trial.

Narjes Modarresi, 32, faces life without parole if she's convicted of capital murder. On Wednesday morning her brother took the stand at the Harris County Criminal Justice Center testifying that she started to unravel mentally in her late teens when he left their native Iran to study in another country.

The defense and prosecutor also questioned a psychiatrist, who went over Modarresi's troubled mental health history. He says she suffers from a severe case of bipolar disorder. He says according to medical records, she felt her baby caused her disorder to get worse.

According to records, the psychiatrist also says she thought murdering her baby was her only option. Because of her mental state, he says she could not see any other options.

The prosecutor painted a different picture while questioning the psychiatrist. She pointed out that the psychiatrist only interviewed Modarresi and went through her medical records to learn more about her mental history. He admitted he did not interview her husband or any other family members.

The prosecutor also made the point that millions of people who suffer from bipolar disorder don't turn into murderers. The psychiatrist agreed.

The prosecutor asked the psychiatrist if Modarresi had the mental capability to realize murdering her son was wrong because of the fact that she tried to cover it up. The psychiatrist responded yes.

According to prosecutors, Modarresi went for a walk with her son in his stroller near her apartment in the 7900 block of Westheimer on April 21, 2010. Modarresi told a neighbor that two black men walked up to her on the street and took the child from his stroller, then drove off in a beige Chevy.

But the story fell apart under police questioning and Modarresi led HPD detectives to the child's body. Police determined the little boy was buried alive and died from suffocation.

Closing arguments are expected on Thursday.