No one disputes that Scott Panetti—heavily armed, head shaved and wearing camouflage—shot and killed his in-laws at their Texas Hill Country home, showering his estranged wife and 3-year-old daughter in blood. Panetti himself acknowledged during his 1995 capital murder trial that he had killed Joe and Amanda Alvarado. Dressed as a cowboy, he acted as his own attorney, believing only an insane person could prove an insanity defense. Jurors convicted him and sentenced him to death, and he is scheduled to die on Wednesday. Panetti’s attorneys are seeking to get him off death row or, in the very least, to...