"The manner in which Texas carries out the execution of human beings is riskier, less transparent, and has less oversight than the euthanasia of cats, dogs, birds, lizards."
Another convicted murderer who was due to be executed on Tuesday -- Paul Warner Powell in Virginia -- meanwhile obtained a stay from the U.S. Supreme Court pending further review.
Troy Davis faces death by lethal injection in Georgia for a crime with questionable evidence, and his sister, Martina Correia fights alongside him while also battling breast cancer.