The mind of convicted College Station killer Stanley Robertson, how it was affected by his upbringing, and how it is now continues to be the focus of the punishment phase of his trial.

After testimony Monday concerning how extreme poverty may have adversely affected his brain, the defense continued to put its experts on mental health on the stand Tuesday.

Robertson, 45, was convicted February 7 of the August 2010 kidnapping and murder of Annie Toliver, his ex-girlfriend's mother. The revenge killing started in the College Station Walmart parking lot, and ended with Toliver's body being dumped in Fort Worth. Robertson says it was all to get back at his ex, Tammy.

Psychiatrist Richard Adler testified Tuesday about studies of Robertson's mind and abilities, ones which he said showed "widespread abnormalities" consistent with mental retardation. In some tests, he scored even lower than diagnosed mentally retarded people have scored.

Because of the capital murder conviction, the Brazos County jury has just two options for punishment: life in prison without possibility of parole or the death penalty.

To earn a death penalty conviction, the State of Texas must convince the jury that Robertson is a future danger, that there are no mitigating circumstances to warrant a life sentence over death, and that Robertson is not mentally retarded.

The latter issue has also been at the forefront of the defense's presentation in punishment, a two-pronged attack that has also included stories of Robertson's sexual abuse as an adolescent and the horrible conditions he experienced as a child.

The prosecution is expected to refute mental retardation with expert witnesses of their own, and has been making the case that many people -- including Robertson's long list of siblings -- have grown up poor and do not commit murders.

Monday, Dr. Jolie Brams, a psychologist for the defense, testified that Robertson's extreme poverty affected the defendant to the point that made him less culpable for Annie Toliver's murder.

The only other witness called Tuesday -- one that will continue her testimony Wednesday morning -- is a neuropsychologist who is discussing IQ scores from Robertson's recent tests.