Arizona plans to execute Clarence Dixon , 66, on Wednesday, even though he is blind, physically frail, and has a documented history of severe mental illness. He is also a member of the Navajo Nation, which opposes the death penalty on cultural and religious grounds. Mr. Dixon was sentenced to death in 2008 for a killing that happened 30 years earlier, while civil commitment proceedings were pending. In 1977, Mr. Dixon was charged with assault for hitting a stranger with a metal pipe. He was diagnosed with severe depression and schizophrenia, adjudicated incompetent to stand trial, and sent to a state hospital for treatment, Slate reports. One of his doctors wrote, “I have a strong feeling that without presence of the mental disturbance, the act of violence would not have taken place.” In January 1978, Mr. Dixon was found not guilty by reason of insanity by then-Maricopa County Superior Court Judge Sandra Day O’Connor, who ordered prosecutors to keep him in custody until civil commitmen...