"This legislation is not about whether to execute mentally retarded murderers," Perry said. "It is about who determines whether a defendant is mentally retarded in the Texas justice system."
The veto came on the last day he could sign or veto bills before they become law without his signature.
The bill would have allowed a jury to determine during the trial's punishment phase whether a defendant is mentally retarded. If so, the person would be sentenced only to life in prison.
|Texas Gov. Rick Perry|
If the evidence had shown the defendant was mentally retarded, the judge would have been required to issue a life in prison sentence.
Existing law takes into account whether a defendant is competent to stand trial, including whether the defendant can aid his own defense and whether a defendant was insane when the crime was committed.
Prosecutors say those factors, and the fact that a jury can consider retardation as a mitigating circumstance during sentencing, are sufficient.
Florida Gov. Jeb Bush last week signed a bill making Florida the 15th state to ban the execution of retarded defendants.
Texas is the country's No. 1 death penalty state. Eight people have been executed this year, 247 since 1982.
Sen. Rodney Ellis, a Democrat from Houston, has said that the state has executed six mentally retarded people since the death penalty resumed. Perry has disputed that, saying no mentally retarded people have been executed.
Perry had said that he wanted to wait for a U.S. Supreme Court ruling on the issue, expected this fall. The high court is expected to rule on a North Carolina case that could outlaw executions of retarded killers.
By Natalie Gott
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