Before Joe Nickell became, in his words, “the world’s only full-time professional paranormal investigator,” he was:

a magician
a blackjack dealer
a private investigator
a poet
a bingo caller
a riverboat manager
a professor of literature
a carousel operator and
a calligrapher.

He listed roughly 1,000 more “personas” on his website.

“God help us if Nickell ever has an identity crisis,” he said a friend liked to joke. “There’ll be 20 of him running around not speaking to each other.”

Mr. Nickell (pronounced nickel) never feared such a crackup. He viewed his various personas as the many facets of a single personality that provided him with investigatory dexterity and made him “a sharp-tongued and amiably pompous old gumshoe,” as The New Yorker described him in a 2002 profile.

Working for the Committee for Skeptical Inquiry, a program run by the nonprofit group Center for Inquiry, and as a columnist for Skeptical Inquirer, the organization’s magazine, Mr. Nickell investigated ghosts, poltergeist activity, apparitions, the Loch Ness monster, crop circles and multiple reappearances of Jesus, including one on a tortilla.

“Some of it is like satire,” Mr. Nickell told The New York Times in 1997, “almost like it’s reached a comic level.”

But in a career that made him notable in both low and high culture — he appeared on the tabloid program “The Sally Jessy Raphael Show” and published books with university presses — Mr. Nickell conducted his inquiries with a “kinder, gentler skepticism,” as he put it, than his contemporaries did.

“I’m not saying there’s a 50-50 chance that there is a ghost in that haunted house,” he told The New Yorker. “I think the chances are closer to 99.9 percent that there isn’t. But let’s go look.”

Mr. Nickell died on March 4 in Buffalo, where he lived, his daughter, Cherette Roycroft, said. She did not specify a cause. He was 80.

Described as “the modern Sherlock Holmes” and the “real-life Scully” (after Gillian Anderson’s skeptical character on “The X-Files”), Mr. Nickell was a disciple of the scientific method, following facts, not beliefs. “In contrast to mystery-mongerers on the one hand and so-called debunkers on the other, I believe that mysteries should actually be investigated with a view toward solving them,” he wrote on his website.

Using skills from his different personas — especially his work as a magician, which taught him how to deceive others — Mr. Nickell solved hundreds, perhaps even thousands, of mysteries, from the paranormal to the historical.

For a show on the National Geographic television network, he offered an alternative explanation for phenomena like the Loch Ness monster, matching sightings of lake monsters to the activity of river otters. Their swimming patterns, he said, created a serpentine effect — the illusion of a long, humpbacked, snakelike creature moving through the water.

In one of his columns, Mr. Nickell described how crop circles, thought to be the handiwork of aliens, could be easily recreated with planks and ropes. Crop circles had become more intricate in recent years because hoaxers were increasingly relying on GPS, he pointed out, not because aliens had improved at geometry.

“He didn’t treat a ghost story as a ghost story or a U.F.O. story as a U.F.O. story,” Kenny Biddle, the chief investigator at the Committee for Skeptical Inquiry, said in an interview. “It was all a mystery. He loved sifting through the evidence, like, ‘OK, what actually happened here?’”

The Shroud of Turin was one of Mr. Nickell’s biggest cases.

Undoubtedly Christianity’s most studied and contested piece of linen, the shroud bears the image of Jesus Christ. But how did it get there? In Popular Photography magazine and later in his book “Inquest on the Shroud of Turin” (1983), Mr. Nickell asserted that the image was an ancient forgery that could be recreated using powdered pigments.

To demonstrate his point, Mr. Nickell made a Shroud of Bing Crosby.

Most of Mr. Nickell’s time was spent chasing ghosts. He never found one.

“A young mother called me once very concerned about the possibility of ghosts,” Mr. Nickell told The Times in 2008. “She was getting strange photographs — a sort of curvy stripe, very white and bright.”

Mr. Nickell looked at her camera.

“Her wrist strap was dangling,” he said. “The flash was reflecting back the wrist strap, and it produced a great number of these.”

Joe Herman Nickell was born on Dec. 1, 1944, in Lexington, Ky. His father, James Wendell Nickell, was a postmaster; his mother, Ella (Turner) Nickell, was a bookkeeper.

As a boy, Joe turned an extra room in his family’s home into a crime laboratory with a microscope, black light and other forensic tools. And one summer, he played a fortune teller at a local carnival.

“While I had good-natured skeptics among my clientele, many others seemed surprisingly credulous,” he wrote in a 2008 essay for the Contemporary Authors Autobiography Series. The experience taught him “about the will to believe and the consequent need for skepticism.”

He graduated from the University of Kentucky in 1967 with a degree in English, and protested during the civil rights movement. In 1968 he fled to Canada to avoid the Vietnam War draft.

Settling in Toronto, Mr. Nickell became a magician at the Houdini Magical Hall of Fame and then worked as a private investigator for the Pinkerton National Detective Agency (now Pinkerton Consulting). In the mid-1970s, he moved to Yukon, where he worked in a casino, took a correspondence course in museology and got into the occasional barroom brawl.

In 1977, after President Jimmy Carter pardoned draft dodgers, Mr. Nickell moved to California. He tried to become a stunt man, but it didn’t work out. He left California to pursue master’s and doctoral degrees in English from the University of Kentucky, finishing in 1987. His specialty was literary mysteries.

During graduate school, he collected antique writing materials, which led him to develop another persona: historical document consultant. He taught himself to make ink and analyze documents with a stereomicroscope. After he published “Inquest on the Shroud of Turin,” the Committee for Skeptical Inquiry hired him as a fellow.

“I became, apparently, the world’s only full-time, salaried paranormal investigator — surely the only one to have been professionally trained as a magician, detective and academic,” Mr. Nickell wrote in his autobiographical essay. “In this role, I travel around the world investigating strange mysteries at the very fringes of science.”

One mystery was more personal.

In an interview, Ms. Roycroft said that in 2003 she confronted her mother, Diana Gawen Harris, with an intuition that the man who had helped raise her was not her biological father. Ms. Harris, who had dated Mr. Nickell when she was a student at the University of Kentucky, conceded that it could be someone else.

Ms. Harris then contacted Mr. Nickell and sent a picture of her family.

Seeing Ms. Roycroft was a revelation for him. “She had the Nickell eyes more profoundly even than I,” he later wrote. They took DNA tests, which confirmed the relationship. In 2006, Mr. Nickell and Ms. Harris married. (His first marriage, to Ruth Everett, ended in divorce.)

“He just loved me,” Ms. Roycroft said. “It was cool to learn about everything he had accomplished, but if he didn’t accomplish anything other than loving me, it was good enough for me.”

Ms. Harris died in 2023. In addition to his daughter, Mr. Nickell is survived by three grandchildren.

The more than 1,000 personas Mr. Nickell listed on his website included family man — and procrastinator, herb gardener, stargazer and science promoter.

“I never really had an identity crisis,” he wrote in his autobiographical essay. “By living many lives in one, I like to think, I have cheated death. So far, so good. I am a lot of happy people.”