During the spring of 2013, thirty-three years after I had met him, Foos called me to say that he was ready to go public with his story. Eighteen years had passed since he had sold his motels, and he believed that the statute of limitations would now protect him from invasion-of-privacy lawsuits that might be filed by any former guests. He was seventy-eight years old, he reminded me, and he felt that if he did not share his findings with the public now, he might not be around long enough to do so. He said he was dissolving the confidentiality agreement that I’d signed in 1980 and gave me permission to write about him and to use all the material he had shown me over the decades. (Later this year, I will publish a book about Foos, a large part of which consists of entries from “The Voyeur’s Journal.” For the use of his manuscript, he received a fee from the book publisher.)

I flew to Denver and met Foos and Anita for breakfast at an airport hotel. He carried a cane, and his thinning gray hair was offset by a gray mustache and goatee. Tightly buttoned over his massive chest was a tweed jacket and, under it, an orange sports shirt. Anita was as he had described her in his letters: eighteen years younger than Gerald, she was a petite, quiet woman with frizzy red hair.

He wanted to show me his collection of sports memorabilia—tens of thousands of sports cards that Anita had organized in alphabetical order. He explained that one of the reasons he was now willing to reveal himself as a voyeur was that he hoped the media notoriety might draw attention to his collection, which he was eager to sell. He believed it was worth millions.

I was more interested in discussing the murder that Foos claimed to have witnessed in Room 10 of the Manor House Motel in 1977. I had let Foos know that, without naming him as a witness, I intended to contact the Aurora Police Department to find out if it had uncovered any new information about the homicide. Foos did not object, saying that he regretted his negligence in the matter. In going public with his story and confessing his failings, he hoped to achieve some sort of “redemption.”

During our breakfast, I showed Foos a letter from Paul O’Keefe, then a lieutenant, now a division chief, of the Aurora Police Department, who wrote, “Unfortunately, we can find no record of such an event.” He had checked several cold-case databases and found nothing. Two coroner’s offices had no information, either. In subsequent phone calls, two former officers said that it would not be impossible for there to be no remaining police records in a “Jane Doe” case such as the one I described: the identity of the victim was unknown, after all, and the crime took place before police departments kept electronic records.

It is also possible that Foos made an error in his recordkeeping, or transcribed the date of the murder inaccurately, as he copied the original journal entry into a different format. Over the years, as I burrowed deeper into Foos’s story, I found various inconsistencies—mostly about dates—that called his reliability into question.

“It seems as if that young woman just fell through the cracks,” Foos said. I thought he might be relieved, but he told me that he had talked to a lawyer. In publicly admitting that he had witnessed a murder and had not acted to prevent it, he said, “I could be an accessory to a crime. I might be convicted of second-degree-murder charges.”

Still, Foos went on, after years of hiding, he was ready to come clean. “Life comes with risks, but we can’t be concerned with that,” he said. “We just tell the truth.”

After the meal, we drove to the Fooses’ house. “I hope I’m not described as just some pervert or Peeping Tom,” he said. “I think of myself as a pioneering sex researcher.” I asked him if he ever considered filming or recording his guests.

“No,” he said, explaining that to be caught with such equipment would have been incriminating, and using it would have been impractical.

He maintained that most men are natural voyeurs. “But most women prefer being watched to watching others,” he said, “which may partly explain why men spend fortunes on porn and women on cosmetics.”

Later, I asked Foos if he had heard of Erin Andrews, the television sportscaster who was secretly filmed coming out of the shower in her hotel room by a stalker who had altered the peephole in her door. The man, who then posted nude footage of Andrews on the Internet, was convicted of a felony and served twenty months in prison. Andrews sued him and the hotel for seventy-five million dollars in damages to compensate for the “horror, shame, and humiliation” she suffered. Last month, a jury awarded her fifty-five million dollars.

Foos had been following the case on the news. His take on it did not surprise me; it echoed the twisted justifications for his own behavior that he’d offered over the years. “While I’ve said that most men are voyeurs, there are some voyeurs—like this creep in the Andrews case—who are beneath contempt,” he told me. “He is a product of the new technology, exposing his prey on the Internet, and doing something that has nothing in common with what I did. I exposed no one. What this guy did was ruthless and vengeful. If I were a member of the jury, I’d unhesitatingly vote to convict.” He insisted that he had little in common with Andrews’s predator.

I asked him why, since he had spent half his life invading other people’s privacy, he was so critical of the government’s intelligence-gathering in the interest of national security. He reiterated that his spying was “harmless,” because guests were unaware of it and its purpose was never to entrap or expose anyone. He told me that he identified with Edward Snowden, the former National Security Agency contractor who illegally released government documents alleging that, for example, U.S. intelligence agencies were tapping the cell phone of Chancellor Angela Merkel of Germany.

“Snowden, in my opinion, is a whistle-blower,” Foos said, adding that instead of being prosecuted Snowden should be praised “for exposing things that are wrong in our society.”

He considers himself a whistle-blower, too, even though, so far, he hadn’t revealed anything to anyone except his wives and me. Asked which “things that are wrong” he wished to expose, he said, “That basically you can’t trust people. Most of them lie and cheat and are deceptive. What they reveal about themselves in private they try to hide in public. What they try to show you in public is not what they really are.”

While he was on the subject of morality, I brought the conversation around to the murder again.

“If I’d known that this particular lady was dying, I’d have called an ambulance immediately,” he said. He had subsequently thought about how he might have saved the woman without incriminating himself. “I would have said, ‘I was walking by the window and heard a scream’—or something like that.”