Is Stanley Robertson mentally retarded? To some, the question may be simple, and the answer may be clear in their opinion. The ultimate opinion of 12 Brazos County jurors on that question will likely be the deciding factor on whether he lives or dies.

Robertson, 45, was convicted Thursday of capital murder in the August 2010 kidnapping and stabbing death of Annie Toliver, the mother of his ex-girlfriend.

In phone recordings played for the jury Friday in the first day of the trial's punishment phase, jurors heard Robertson tell ex Tammy Toliver that her abandonment of him was the catalyst for the defendant attacking Annie in the parking lot of the College Station Walmart. The victim was stabbed 31 times with a five-inch utility knife Robertson had bought less than an hour earlier, causing wounds in the eye, neck and abdomen, among other places. She bled to death over upwards of six hours, an autopsy revealed.

On the very first day of the trial, the defense noted that they would work to show Robertson is mentally retarded. The U.S. Supreme Court ruled in the Atkins v. Virginia case that those shown to have the disorder should not be executed. It's a violation of the Eighth Amendment, the ruling said.

The route to proving it is one that can prove interesting. There are three prongs of mental retardation according to the Diagnostic Statistical Manual of Mental Disorders.

- an IQ below 70, or below 75 within a margin of error
- clear deficiencies in adaptive behavior
- the low IQ and deficiencies clearly showing up before the age of 18

Defense attorneys for the last Brazos County defendant facing the death penalty, Stanley Griffin, made the mental retardation argument, bringing forward experts in the mental health field who said Robertson tested low in IQ tests and was deficient in a variety of behavioral areas, all before 18. The jury believed the prosecution's experts that countered, and Griffin sits on Death Row.

Throughout the first five days of this latest trial, prosecutors have tossed in questions to those who have known Robertson for extended periods. Is he gullible? Naive? Able to cook and clean for himself? Dress himself? Handle his own bank account? The answers have been yes. While only a fraction of what would be needed to disprove the defense theory, it laid the foundation for the fight the State of Texas will put up.

The prosecution could wrap up its first set of witnesses in punishment Monday, leaving the defense to bring its experts and those who have been the recipients of good deeds and acts by the defendant, the standard practice in this phase.

The State of Texas will then have its chance to bring experts of its own. The lawyers must show Robertson is a clear danger to others if allowed to live, that there are no mitigating circumstances that would prevent his execution, and that he is not mentally retarded. Then and only then would he face the ultimate punishment. Otherwise, he would be sentenced to life in prison without the possibility of parole.

The first day of the punishment phase played to the danger aspect. After dumping Annie Toliver's body in Fort Worth, he led police on a chase through the city. Following through on his claims to harm any law enforcement and himself if they attempted to take him, Robertson rammed his SUV into an FWPD patrol car, seriously injuring the officer driving.

One month earlier, Robertson had put a knife to Tammy Toliver's throat in front of her three children. He was arrested after a hostage situation in their College Station apartment. Robertson would later say the fact that Tammy wouldn't visit him in jail or return his calls led him to attack her mother.

The punishment phase is expected to last through this week, possibly into next.