For years, Mr. McDowell was identified as black. But recently the authorities acknowledged that Mr. McDowell was white, a critical mistake that dispelled the white supremacist label, Mr. McClain said.

“It just didn’t happen the way the prosecutors say it did, and the mistake about the race changes the whole theory of the case. And if he were to go to trial right now, he would not get the death penalty under the new rules,” he said.

Mr. Asay denied shooting Mr. Booker and offered his version of events for Mr. McDowell. In a jailhouse interview with the Jacksonville television station News4Jax, he said he shot Mr. McDowell — whom he knew as “Rene” and had encounters with — in an inebriated rage.

“I’m very sorry for what happened. Rene was actually a friend of mine, I don’t know what happened,” he said. “I did not go out with intentions of having a problem with anybody. I just got drunk.”

He said his white supremacy tattoos were for his protection in a Texas prison, where he served time on an unrelated charge before the Florida murders.

“I was 19 years old, forced to survive in a hostile prison environment, and I got these tattoos in that environment so that I could blend in, so that I could be safe in that environment,” he said in the interview.