Executed
James D. French
James D. French was executed by electrocution in Oklahoma on August 10, 1966, according to a 2013 Oddee article. The article says he was the last person put to death under the state's laws before the U.S. Supreme Court's 1972 Furman v. Georgia decision. It reports that his final words were a quip about a headline.
Cause of death, as reported: Executed by the state
Reported by: Oklahoma state prison authorities (the agency that held him). The only account of how this person died comes from the agency that held him.