WASHINGTON  Ronald Kempfert was a young boy in 1975 when his father was sent to prison for murder, and they had no contact for 28 years.

Then, in 2003, Mr. Kempfert heard from a lawyer who had been looking into the case. “Your father is innocent,” said the lawyer, Larry A. Hammond. “And we’re pretty sure your mother framed him.”

That would seem a lot to digest, but Mr. Kempfert, 42, said he felt no hesitation. “My reaction was that it didn’t surprise me,” he said. “She’s my mother, and I love her. But I think she’s capable of anything.”

Mr. Kempfert is now certain that his father, William Macumber, is innocent. Arizona’s clemency board, citing Mr. Kempfert’s “very moving testimony” and saying there had been “a miscarriage of justice,” unanimously recommended last year that Mr. Macumber be freed.