“With ‘The Thin Blue Line’ there was a feeling of closure,” he said, pointing out that Randall Dale Adams, sentenced for the murder of a Dallas police officer, was exonerated and released from prison a year after the movie came out. But for the MacDonald case, “the more I investigated, and I investigated for years, you would see the evidence pointing in one direction rather than another,” he said. “I know what happened. In this case it’s not that it became muddier. There is always a hope. I felt so close, but I couldn’t bring it to some satisfactory resolution.”

He does argue convincingly that a witness, Helena Stoeckley, a known drug user, confessed repeatedly that she was the woman in the floppy hat mentioned by one of the investigators, who spotted her in the area on the way to the crime scene. But when she was called to testify in the case, she said she was never there. (Ms. Stoeckley died in 1983.) Mr. Morris uncovers an episode of her supposed intimidation by prosecutors, which may be part of the evidence presented this month at Mr. MacDonald’s hearing. “It would be wonderful to have interviewed her and so many others on film,” Mr. Morris said wistfully.

If the dead aren’t talking, some of the living take a beating in Mr. Morris’s book. Although he says he holds the tenets of journalism in high regard — the pursuit of truth and the music of fact — he finds two of its practitioners highly wanting with respect to the MacDonald case. In the book he suggests that Mr. McGinniss, who lived and worked next to the defense team, was callow and opportunistic, a writer who traveled “a slippery slope of tergiversation, opportunism and self-interest.” This is famously well-covered territory, of course, in Janet Malcolm’s New Yorker article and later book, “The Journalist and the Murderer” (1990), which both begin with this indelible line: “Every journalist who is not too stupid or too full of himself to notice what is going on knows that what he does is morally indefensible.”

Mr. Morris finds some of the basis of her critique — that journalism itself is morally compromised and built on deception — appalling. “Janet Malcolm wrote about Joe McGinniss as if he were representative of journalism per se, and I respectfully disagree,” he said. “There was something very pathological in the relationship between McGinniss and his subject.”

“I despise versions of postmodernism that suggest that there is no such thing as truth, that the truth is up for grabs, relative and subjective,” he added. “Narrative does not trump all; it does not trump the facts. The facts are immutable. You may not be able to apprehend them or they may be elusive, but they are there.” (Ms. Malcolm declined to comment because she has not read Mr. Morris’s book.)

Mr. McGinniss said that Mr. Morris did not attempt to contact him, and Mr. Morris said that Mr. McGinniss did not respond to his e-mails. But Mr. McGinniss, whose book “Fatal Vision” is about to be reprinted and issued for the first time as an e-book, said he is comfortable with his conduct and conclusions.

“There is no question in my mind that he did it, and that it was proved in a court of law, and that every court that has looked at that jury verdict has upheld it,” he said, adding that he has been subpoenaed to appear at the hearing this month in North Carolina and that he “looks forward to going wherever I need to to play whatever small role I can play in keeping him where he belongs.”