But Baldassano again showed jurors surveillance video of Tata shopping at Target during the time her home was on fire.
As the video played, Baldassano said Tata never seemed rushed, even after remembering the stove was on.
"She doesn't seem to care at all she left those kids home alone," he said. "She's just hanging out, going to Target."
Tata had initially told investigators she was at home when the fire began.
Jurors can convict Tata of several, less serious charges in this trial: recklessly causing serious bodily injury to a child, abandoning a child, endangering a child and causing serious bodily injury to a child by criminal negligence. The lesser charges carry prison sentences ranging from six months to 20 years.
Convincing jurors that Tata was responsible for leaving the burner on could be important for prosecutors in getting a felony murder conviction. Prosecutors do not need to show that Tata intended to harm the children, only that the deaths occurred because her actions put them in danger.
Under Texas law, a person can be convicted of felony murder if he or she committed an underlying felony that led to the death.
During the two-week trial, prosecutors presented about 30 witnesses, including neighbors who testified about hearing the children crying during their unsuccessful attempts to rescue them during the blaze. Parents of the children who died or were injured testified that they had trusted Tata, believing she was qualified.
After the fire, Tata fled to Nigeria but was captured after about a month and returned to the U.S. in March 2011. She has remained jailed since then. Tata was born in the U.S. but has Nigerian citizenship.
In addition to the felony murder counts, Tata was also indicted on three counts of abandoning a child and two counts of reckless injury to a child.
Associated Press writer Nomaan Merchant in Dallas contributed to this report.