For 15 years his suburban Virginia neighbors believed he was James Dee Francis Sheker, a good family man and a successful engineer who waved to them each morning on his way to work in a Jaguar convertible.

To Oklahoma neighbors he was Michael Carr Speer III, a congenial bachelor with a genius IQ and a Stanford Ph.D. As Speer he was about to close a million-dollar deal.

California neighbors knew him as Dallas Dean Rust, the wheeler-dealer operator of a gold mine in French Gulch. He drove a pickup truck, wore a Stetson hat and carried a .38.

In each case the man the neighbors knew did not exist.

There is no record of the engineer's birth in any of the 50 states and two of his bridges collapsed. The real Speer was found in a shallow Oklahoma grave, three bullets in his head. As for Rust, a drifter from South Bend, Ind., he was last seen in Florida.

Then who is this man? A man who has juggled identities, birthplace, age, nationality and profession for so many of his 50 years that he has become one of the great impostors of the century?

"It has been a trauma. Some people say I am a manipulator, a master of disguise. I am a real person. I wasn't hatched. I breathe air. I drink water," he said in a recent interview. He speaks with the trace of a Spanish accent. His face is oriental, with high cheek bones, quill-straight black hair and dark engaging eyes. Around his neck he wears a Star of David and on his little finger a Mexican gold coin. He is muscular with a large circular scar on his back. The middle and ring finger of his left hand are mere stubs.

Again he is calling himself "Jim Sheker," but he says he does not recall the last time he said his real name aloud.

There is nothing of the slick confidence man about him. He is polite and shy with an almost professional air. Monday he is to go on trial for the murder of Speer, a soft-spoken Washington scientist whose identity Sheker assumed.

Sheker's story, then, comes not from his own lips but from those of his family, friends, colleagues, and a legion of FBI agents, police, private investigators and reporters who have tried to look behind the many masks of Jim Sheker.

It was in early 1960 that a military transport from Okinawa touched down in California with a dark-skinned 30-year-old passenger aboard. His name then was James Sheker. From California he took a Greyhound that let him off on U.S. 1 in Alexandria. When he stepped off the bus, he was wearing a Navy commander's uniform, carrying a duffel bag and holding his military orders in his hand, recalls his first wife, Arlene. She was startled. She knew he had not been in the military. He told her it was the quickest way he could be with her.

A year earlier they had met in Okinawa and fallen in love. "Jim," she remembers, was an exciting man and a person of mystery. He told her he was an engineer with the U.S. government. She had heard him speak French, Chinese, Japanese, Spanish, English and Philippine dialects. He was a gourmet cook with a flair for curries and other Oriental dishes. He was a world traveler. And he was an incurable romantic. In their year apart he had mailed her blades of grass with "I love you" incised in painstaking detail.

He had told her he was born in Montreal. Unknown to Arlene, the only connection he had with Canada was his engineering certificate, which belonged not to him but to a Canadian engineer. Why he left Okinawa when he did is unclear, but Lynn Larsen, a close friend of his who also lived on Okinawa, recalls his telling her that he had to leave the island in a hurry, that he was "under some kind of a cloud."

Sheker moved into a small apartment on Washington's 16th Street. Arlene recalls him lying on the floor running his index finger ove a map of the United States, looking for a town to claim as his birthplace. She remembers him mentioning a small town -- Richmond, Texas -- where fire had gutted the courthouse and destroyed records. For the next five years Sheker told friends, associates and the U.S. government that he was born in Richmond, Texas.

In December 1960 Sheker lost two fingers on his left hand. He told his wife it was an industrial accident. He later told friends it was a nuclear accident. Whatever the cause, he spent several weeks in Prince Frederick [Md.] Hospital. There he began an autobiography that assiduously avoids giving any clues as to his true identity or background.

"Many men and women are content with their lives as they are. They manage amazingly well, far better than I could it seemed to me. Looking at their lives from the outside with envy and admiration I observe the perfection of their smoothly ticking days," he wrote in the unfinished manuscript.

A darker side of Jim Sheker emerged. Arlene remembers the gentleness sometimes giving way to fury. Twice he broke his hand putting his fist through the wall of their Alexandria mobile home at the Oak Grove Trailer Park. Once he chopped down a tree in a fit of rage. Capillaries in his nose burst with rage.

Arlene recalls that by mid-1965 Sheker refused to discuss his work with her, saying it involved construction for the government at a top-secret site. Sheker returned home wearing government identification tags and voice printouts he said were necessary to enter underground facilities.

Each Saturday he put on a Navy commander's uniform and disappeared for the day, saying he had to report to Patuxent Naval Air Station to flight exercises. Arlene was afraid to ask questions. Things didn't jibe, she said. Their marriage was disintegrating. In mid-1965 she called the FBI and told them of her husband's naval activities.

On June 24, 1965, two FBI agents interviewed Sheker at his home at 6360 Frontier Dr. in Springfield, Va. According to an FBI report, Sheker told the agents he was not a U.S. citizen. In his wallet they found two Defense Department identification cards. Sheker told them he received the cards as a civilian employe on U.S. military bases in Okinawa in the 1950s.

He told the agents he bought the Navy uniform in a pawn shop, that he wore it because he liked the way people looked at him when he was in uniform. The FBI ran an extensive check of Sheker's background. They found no record of his birth or of military or civil service.

But the FBI brought no charges against Sheker. Agents said federal prosecutors would be reluctant to bring the case to court unless they could show Sheker had benefited monetarily from his impersonation. Sheker continued to wear his Navy uniform undisturbed for the next 10 years.

He told friends the CIA had intervened on his behalf and had cautioned the FBI "to leave this one alone." His story of a CIA connection was nothing new. Since Okinawa days he had been telling friends that the agency provided him new identities whenever needed as well as the military identification necessary to carry out his assignments.

Sheker never forgave Arlene for calling the FBI. In 1978, 13 years after the FBI incident and their divorce, he wrote her from an Alexandria, Va., jail where he was being held for kidnapping Speer. "You started this whole nightmare when you called the FBI about my Naval activities . . . . From that time you started a chain reaction blowing my cover. I left the Agency [CIA] without any choice.It finally led to this."

Sheker married Dorothy Jennings in 1966. For the next three years they lived in the Yorktown Square Apartments in Falls Church leading an ostensibly normal suburban life. But Sheker's talk of the CIA continued.

Most neighbors were convinced Sheker was with the CIA. He never went into detail about his work for the "company," as he sometimes called it. Instead he casually displayed a CIA ID card or dropped hints and half-completed sentences, leaving the rest to his listener's imagination. His singular appearance, his wide range of languages, and his familiarity with faraway places lent credibility to his voice.

On one occasion in mid-1975, Michael Ames, a Maryland executive and employer of Sheker's, went as Sheker's guest to an invitation-only dinner at the Army-Navy Club at Ft. Myers to meet the joint chiefs of staff. Ames recalls Sheker displaying an Air Force ID at the door and being ushered in to the select affair. Later he and Sheker stood in a reception line and were presented to the nation's top generals.

Sheker's fascination and expertise with guns were also well known to neighbors. He seldom went anywhere without his .38 tucked in his coat. He even carried it to his friends' homes for dinner parties. Later, at his Lambeth Square home in Centreville, Va., he displayed a dozen exotic guns in a glass case.

On Aug. 4, 1975, Sheker returned home holding his left arm. It was bleeding. He had been shot, he told his wife and a neighbor, by a CIA agent who had intended to scare him off. He reported the shooting to Fairfax County police as an accident. He said he had been cleaning one of his guns and that it had gone off.

A 1978 FBI report notes that while Sheker had never been in the U.S. military, "he has definitely at one time flown the F-9 aircraft." In an effort to trace Sheker's background, the FBI requested a Defense Department list of all countries to whom the United States had sold the sophisticated Panther jet, a carrier fighter.

William Ausley, a car salesman who sold Sheker a Jaguar and who was himself a Panther pilot in the Korean War, remembers Sheker discussed the operation of the aircraft with him in great detail. He went away convinced Sheker had piloted the aircraft.

But to most of Sheker's neighbors, he was just another suburban dweller. He was well-liked, given to entertaining, selfless with his time and always good for a spellbinding story. Each Sunday he attended the Christian Assembly Church in Vienna.

No one questioned his success as an engineer. Neighbor Jerry Hargis recalls Sheker this way:

"He was a construction engineer. He got up early and went to work. He came in late. Steady. Open. Honest. Apparently he was just a good engineer because I think he was working on some rather important projects. I think he was employed at one time on the restabilizing of the Capitol facing and on the Washington, D.C., Metro project."

By 1970 Sheker's income had improved markedly, and he moved into a Centreville townhouse. He and his wife, Dorothy, took frequent trips around the country, including weekend getaways in private planes piloted by Sheker. [D.C. police say there is no record that Sheker had a pilot's license.] He drove a new Jaguar convertible XKE, a 450 SLC Mercedes-Benz and a Chrysler.

How did he get by at work? "He always knew the right buzzwords. He knew all the words you're supposed to use," said Ed Daniels, a former vice president at Montclair Development Corp., where Sheker worked as chief engineer for two years. "He was the ultimate great impostor."

Like many of Sheker's former employers, Daniels credits him with a photographic memory. Sheker was a regular at area libraries where he took out texts on subjects his employers assumed he already knew. In addition, Sheker was careful to stay in a supervisory capacity, maintaining a distance from front-line decision-making. He approved others' work.

Sheker had told Daniels he had a master's degree from the Colorado School of Mines and was working towards a Ph.D. in sanitary engineering from Virginia Polytechnic Institute. When Sheker informed his colleagues that he had completed his Ph.D. requirements, they were so impressed they held a catered surprise party for him at the Montclair Country Club and gave the entire staff the day off. Sheker showed up in cap and gown, recalls club manager Art Colasanti.

Later Daniels learned VPI did not offer a Ph.D. in sanitary engineering and had no record of Sheker's enrollment. Nor was there a record of him at the Colorado School of Mines.

Sheker's credibility as a professional engineer ran into trouble in late 1974. Daniels discovered there had been enormous cost overruns and defects in engineering. He checked Sheker's engineering credentials.

His engineering stamp was number 3714. That number, according to the Virginia Board of Registration, belongs not to Sheker but to a retired engineer now living in Homesdale, Pa. The state board had no record of Sheker as a professional engineer.

In April 1975 Daniels fired Sheker. Prince William County police issued an arrest warrant on Nov. 26, 1975, charging Sheker with fraud. Sheker had already vanished from the state.

Since than a 40-foot bridge and a 20-foot bridge Sheker had built at the Montclair golf course have collapsed, according to Daniels. The wood bridges were apparently based on plans in an old Army manual. They would have supported a tank on dry land but they were not designed to stand in water, said Daniels.

On May 1, 1975, Sheker joined Ames Associates, an executive placement firm in Bethesda that recruits engineers for the mortgage banking and construction industry.

"He was affable, intelligent and very knowledgeable on all subjects," recalls Michael Ames. "He certainly sold everyone a bill of goods." Sheker had convinced Ames he was a Sioux Indian with CIA connections.

According to Ames, shortly after joining his firm, Sheker was introduced to Farlan [also known as Michael Carr] Speer, a quiet 42-year-old Ph.D. living in northwest Washington.

Speer, a man who could work a New York Times crossword puzzle in 10 minutes and had attended the University of California on a scholarship at age 15, had been unemployed for two months. He was just waiting for the right job to come along.

It was Sheker who worked with Speer and handled his employment file, recalls Ames. Sheker introduced Speer to Ames, and the three spoke together for several minutes before Speer and Sheker took up details of employment between themselves.

Sheker denies ever meeting Speer.

In October Sheker left Ames Associates. With him he took Speer's file, according to the FBI. A Centreville neighbor of Sheker's says she remembers Sheker sitting in his living room examining the Speer file in front of her and his wife Dorothy. He told them Speer was to be his new identity and that the CIA had provided him with the material, the neighbor recalls.

On the evening of Nov. 17, 1975, the real Speer called his parents in Chicago and told them he had a job offer from a man named "Jim" who promised him a $50,000-a-year position in Haiti. First Speer would have to go to Oklahoma for orientation, he told his parents. He sounded terribly excited, recalls his father, Paul Speer Sr.

On Nov. 18, 1975, Ruth Jahoda, a close friend of Speer's, drove Speer to Dulles Airport for a 6 p.m. flight to Tulsa, Okla. It was the last time anyone was to see Speer -- until his body was unearthed in a red clay grave outside Guthrie, Okla., 2 1/2 years later.

One month before Speer's departure for Oklahoma, Sheker took out an Oklahoma driver's license using Speer's date of birth and Social Security number. Instead of listing Speer's 6-foot 1-inch frame, blond hair and blue eyes, Sheker wrote down a description of himself -- 5 feet 9 inches, black hair and brown eyes. In short, Sheker became Speer.

Sheker went to banks, employers and neighbors telling them he was Michael Speer. Along with Speer's name, Sheker claimed Speer's impecable academic credentials and background.

"I don't deny I used Michael Carr Speer's identification but I didn't kill him," said Sheker in a recent interview.

Sheker refuses to say how he got Speer's identification or why he found it necessary to use another identity. He has told friends and associates it was the CIA who had directed him to assume this new identity. Sheker told them that the CIA had erred in giving him Speer's identity, that the agency had believed Speer was without family and was himself affiliated with the intelligence community.

William Colby, former CIA director, says the identity switch described by Sheker "does not ring true," that it simply is not how the agency provides new identities to its agents. He called Sheker a "clear fake."

A few days after Speer's arrival in Oklahoma Sheker registered at the Guesthouse Motel in Oklahoma City as Speer and, according to FBI reports, gave away several items of clothing that were too large for him. Among these, reportedly, was a white sweater like that believed to have been worn by Speer when he left for Oklahoma.

Sheker acknowledges he may have given some sweaters away. "They stretched in the wash" he said.

On Nov. 21 Sheker telephoned Patrick O'Connor, a close friend from Virginia who was then living in Florida. He told him he had killed a CIA courier in a gun battle, according to O'Connor's testimony in a preliminary hearing earlier this year.

O'Connor said Sheker had told him that the courier failed to recite the code word and drew a gun on him. Sheker, according to O'Connor, said he then shot and killed the courier.

The next day O'Connor flew to Oklahoma and was met at the airport by Sheker. Sheker reportedly drove him to a remote tract of land a few miles outside of Guthrie. On the way he told O'Connor the courier was to have provided him with a new identity. Sheker described how he neatly placed three bullets in the courier's head and remarked at the triangular pattern they formed.

When Sheker and O'Connor arrived at the grave, O'Connor testified, they heaped stones and branches on top of it. "There was a space of newly turned earth, approximately 6 feet long and 3 feet wide," he said.

It was not until April 19, 1978 -- 2 1/2 years later -- that O'Connor notified the FBI about the episode, and led FBI agents to the site. Beneath a foot of damp red clay in the bowl of a steep ravine, agents uncovered a badly decomposed body of a man. From dental records experts identified the corpse as Speer.

Even today the outline of the grave is visible, and a few small bleached bones -- perhaps only those of a small animal or bird -- appear against the red clay. The body was cremated, but the skull sits in a cardboard box in the courthouse, probable trial evidence.

In the intervening two years that Speer had been missing, the impostor Sheker had approached utilities companies throughout the Southeast and West with what he described as a revolutionary process he had developed for extracting gas from coal. At the same time he was a vice president with Drum Construction Company, a large multi-state firm that featured Speer and his Ph.D. on its letterhead.

Sheker met repeatedly with executives of Oklahoma Gas and Electric Company, who extended him VIP treatment and escorted him through their facilities. They even offered Sheker the use of one of their plants to test his unique process. At one point, according to the FBI, Sheker -- known to them as Speer -- held an audience of the company's Ph.D.'s spellbound as he described his innovative catalyst that would make the gasification of coal cheap and easy.

"Obviously they would have thrown me out of the office if I had not known what I was talking about," bragged Sheker at a recent interview.

But while Sheker's plans were taking shape, two men he didn't know were closing in on him. One was Mike Fenske, a Colombo-like Washington cop who was mesmerized by Sheker's many identities and had devoted hundreds of off-duty hours trying to run him down.

The other was Paul Speer Sr., father of the missing scientist. Speer had received a mysterious phone call from a man with a heavy accent who told him not to worry about his son. The caller, who identified himself as Dr. Morgan, said his son could not be reached but that all was well and Speer would be in touch in a few months.

Paul Speer hired an Oklahoma private eye, Robert Cunningham, to find his son. For Speer it had been a nightmare without end. On July 30, 1976 the nightmare took an even more bizarre turn when Cunningham sent two detectives to interview the man who had taken his son's name and identity.

Sheker told the investigators he was Speer and gave as his birth date and Social Security number that of Speer. They recorded the interview. Paul Speer later listened to the tape recording and identified the voice as that of "Dr. Morgan." The next day the detectives returned to the house for another interview. Sheker had gone, leaving only a bathmat behind.

Sheker was arrested April 12, 1978, in Yreka, Calif., by FBI agents and local police who surrounded the motel where he was staying. When arrested he was carrying a .38 in his down jacket. On his finger was a Stanford ring, class of 1970, with the initials "MCS" inside it.

In his wallet was a complete set of identification for three people: Speer, George William Johnstone and Dallas Dean Rust. He had stayed with Johnstone in Barrie, Ontario, several months earlier. Johnstone says he does not know how Sheker got his identification cards.

But it was under the name of Dallas Dean Rust that Sheker had been living from mid-1977 to mid-1978. As Rust, he had operated the Washington Gold Mine in French Gulch near Redding, Calif. He lived with 23-year-old Deanna Brobst, who knew him only as Rust.

Sheker had told her his parents had been killed in a car accident, that they were wealthy oil people and that they had left half their estate to the University of Oklahoma. She described Sheker as easy-going, except at night when he became nervous and stood at the window staring out into the dark. He was never without his gun. He was charming.

"He always wore this gold wedding band. He said his wife died three days after they were married and he wore it as a reminder. I guess I was kind of blind not to put all these things together," she said.

The real Dallas Dean Rust, according to relatives, is a drifter from South Bend, Ind., who was last seen in Florida.

After his arrest in California, Sheker spent a year in the Logan County jail in Guthrie, Okla. He was released on April 13, 1978 after posting a $20,000 bond. During his time in jail he established himself as a favorite of the guards. He was permitted to walk about the facility freely. He was made a trustee of the jail, baked cookies and cakes for the guards and even cleaned their guns.

Six days after he was released Sheker appeared in Redding, Calif., claiming he was an IRS agent. Federal officials prosecuted him for that imposture, leading to his conviction last month in a Sacramento federal court and a three-year prison sentence.

Prior to that reverse Sheker was living in Redding, driving around town in a Cadillac and boasting to his friends that he was on the verge of closing a multi-million-dollar deal.

He seemed full of confidence. "I will not be a burden to the state, let me put it that way," he said with a smile.