He strolled into the police station in Chelsea on Jan. 4 wearing a Harvard sweatshirt, a “Wounded Warrior” cap and military dog tags dangling from his neck. He said he was Jeremiah Asimov-Beckingham, a veteran of Afghanistan, wounded in combat, now working as an executive for an airline. He had come to the station to pick up his car.

His new BMW had been impounded, he believed, as evidence in a random crime. But it was a ploy. The police were hoping to lure a man suspected of forging checks in Cambridge, Mass., to steal $70,000 and the BMW, which they had tracked to a Manhattan garage. They put Mr. Asimov-Beckingham in handcuffs and charged him with larceny.

Investigators soon learned that the man’s name was not Asimov-Beckingham. He had never been wounded in combat, nor had he ever served in the military. New York detectives and Homeland Security agents found an Indiana birth certificate in his immigration file showing his name as Jeremy Wilson, born in Indianapolis in July 1973. It was the oldest document in the file, so they charged him under that name.

Still, his identity was a puzzle. He had spent 25 years stealing Social Security numbers and fabricating new aliases, leaving behind a thicket of confusing and falsified records. Six weeks earlier, he had been released from a federal prison in New Hampshire, where he had served six years for identity theft as Jeremy Clark-Erskine. But he had more than 27 aliases in five states. His birth certificate had been altered several times. Even his citizenship was in doubt. He had been deported more than once as an illegal immigrant. Now he is at Rikers Island, awaiting trial.