Texas to Execute Man Deemed Mentally Retarded Tomorrow's penalty would run counter to Supreme Court ruling By Matt Cantor, Newser User Posted Aug 6, 2012 2:26 PM CDT 78 comments Comments A Texas man diagnosed with mental retardation is set to be executed tomorrow. (Shutterstock) (Newser) – A Texas prisoner diagnosed as mentally retarded is set for the death penalty tomorrow—despite a 2002 US Supreme Court ruling barring mentally retarded people from execution. The court decision left states some leeway in carrying out executions, and Texas controversially continues to use its own definition of mental retardation, the Guardian notes. Marvin Wilson doesn't fit that definition. After extensive testing and interviews, a neuropsychologist diagnosed Wilson, who faces punishment for the killing of a police informant, with mental retardation. But Texas' definition, which a disabilities advocacy group calls "impressionistic," uses a character from John Steinbeck's novel, Of Mice and Men, as a barometer for retardation. The state did not conduct cognitive testing on Wilson. If he "is executed on Tuesday, Texas will be rendering the US Supreme Court's Eighth Amendment prohibition on the execution of mentally retarded prisoners a prohibition in name only," says Wilson's lawyer, who is seeking to delay the execution so the matter can be considered.