A paper-thin slice of thigh bone -- "a piece of Josef Mengele" -- sits on the piano in Ellis R. Kerley's University Park living room. It is one clue of many -- including a fractured right hip bone, a damaged left cheek, a 47-year-old photograph -- that led Kerley and a team of 16 other scientists to conclude that the skeleton they examined in Brazil last week was that of the notorious Nazi war criminal.

"I feel quite confident this is indeed Mengele," Kerley, a professor of anthropology at the University of Maryland, said yesterday, hours after his return from the celebrated investigation in Sao Paulo, Brazil. " . . . It's a little awe-inspiring when you realize this is a guy who slaughtered 250,000 individuals."

The conclusion was made only at the end of nearly a week of meticulous study by teams of American, German and Brazilian experts who sifted through crumbling bones, studied handwriting and fingerprints and fed their findings into a computer at the Medical Legal Institute in Sao Paulo.

The American team that traveled to Brazil June 12 doubted that it would find the remains of Mengele, Kerley recalled. Earlier this year at the request of the U.S. government, Kerley had studied a photograph of a man living in South America and concluded there was a 95 percent chance the man was Mengele.

The American scientists knew that all evidence had to agree, Kerley said. Had dental records indicated a filling in a tooth, for example, where they found none, all other resemblances would be meaningless.

But "the more we looked, the less skeptical we became," he said. There was "too much coincidence."

Kerley, 60, began his work by reassembling the bones of the man originally believed to be Wolfgang Gerhard, the name that appeared on the 1979 death certificate. Like his colleagues, Kerley labored at the modern medical center not far from the Brazilian cemetery where Mengele's bones were discovered.

"We had no idea what we were looking for . . . ," Kerley recalled. "The first thing we wanted to know was if there were any old fractures."

In fact, the right hip bone they were studying was fractured, coinciding with information that Mengele had injured his leg in a motorcycle accident at Auschwitz.

There was more evidence: The skull showed a space between two front teeth, the same space scientists could see in a 1938 military photograph of a smiling Mengele.

The left cheek bone showed a fistula, or small hole. That finding agreed with information from Wolfram and Liselotte Bossert, the Austrian couple who sheltered Mengele for several years in Brazil. They told scientists that the man who stayed with them had complained of hair growing inside his mouth, a possible symptom of the fistula. Beard hair could enter the mouth through the fistula, Kerley said.

The Bosserts had also said the man they housed had complained of arthritis, and the bones showed evidence of the same disease.

Skeletal measurements also indicated a man matching Mengele's small stature; the 1938 photographs showed ear shape and two facial moles identical to those in photographs taken of the man who lived with the Bosserts.

Kerley, who in 1965 developed a method of measuring age by studying bone slices through a microscope, applied his process to two sections of the thigh bone, one of which now graces his living room piano.

"There were no one or two things" that sealed the conclusion, Kerley said. "It kept building up . . . . It was exciting. It was good news that all of us, working from different points of view, were swept up in the growing conviction. Everything pointed in one direction. There was nothing that excluded it."

Toward the end of the week, the American scientists watched as the German team displayed its work: superimposition of photographs of Mengele over photographs of the exhumed skull.

After days of dodging reporters and television cameras, the scientists could finally make their dramatic announcement: "Within a reasonable scientific certainty," the bones they had reassembled were Mengele's.