A psychologist for the defense team of convicted College Station killer Stanley Robertson began the third week trial Monday discussing the defendant's extreme poverty growing up.

Dr. Jolie Brams discussed violence Robertson dealt with, his exposure to pesticides working in Alabama farm fields, poor nutrition for his mother before his birth and for him after birth, a lack of toys or books, frequent school absences, and an overworked and uneducated mother as being among the many reasons Robertson's development was stunted.

Robertson was convicted February 7 for the August 2010 kidnapping and stabbing death of his ex-girlfriend's mother, Annie Toliver, who was taken from the College Station Walmart parking lot. Her body was dumped in Fort Worth, where Robertson later led police on a chase, one that ended with Robertson intentionally slamming his SUV into a patrol car.

The defense for Robertson will continue to argue their client is mentally retarded, thus ineligible for the death penalty by virtue of a U.S. Supreme Court ruling. But they are also working to convince the jury that mitigating circumstances -- his poor childhood and being sexually abused as an adolescent among them -- should keep the jury from choosing the ultimate punishment.

The prosecution on cross examination of Brams questioned the extent of the research she did, including the fact that she questioned no members of the Toliver family. They also continued to assert that many people go through poverty and abuse in their childhood, but do not commit murders.

The jury must unanimously believe Robertson, 45, is a future danger to others, that there are no mitigating circumstances to prevent his execution, and that he is not mentally retarded in order to decide on the death penalty.

When they call rebuttal witnesses -- expected later this week -- the prosecution is expected to call a psychologist to refute the defense's expert and state Robertson is not mentally retarded. They have also argued that many other people grow up with the circumstances Robertson had in his youth and did not commit heinous crimes.

The only other witness called Monday was a former Texas Department of Criminal Justice administrator, who discussed the conditions Robertson would spend the rest of his life in if he were to be sentenced to life in prison without parole.