Marvin Wilson, 54, was put to death for the 1992 death of a police informant.
But, anti death penalty advocates say Texas executed a mentally challenged man.
Attorneys for Wilson say he had an IQ of only 61 and therefore should not have been eligible for the death penalty.
The Supreme Court ruled ten years ago that states could not execute someone with diminished mental capacity. But, they left it up to the states to determine their own standards of what that means.
Headlines across the country decried the state's execution of Wilson.
Some articles claiming Texas flouted the Supreme Court's ruling against executing the mentally challenged.
Prosecutors say Wilson's career of crime proves he is not mentally diminished. They say he was very calculating.
But Amarillo civil rights attorney Jeff Blackburn says the execution is another black eye for Texas' judicial system.
Texas has nine more executions set for this year including an Amarillo man.
John Balentine is set to be put to death August 22nd for the 1998 murders of three teenagers.