Like Mr. Bundy, Mr. Madoff used a sharp mind and an affable demeanor to create a persona that didn’t exist, according to this view, and lulled his victims into a false sense of security. And when publicly accused, he seemed to show no remorse.

Television footage of Mr. Madoff entering his apartment building on East 64th Street at Lexington Avenue after federal authorities charged him with fraud in December doesn’t seem to show a man exhibiting any sorrow or regret. With a battery of reporters asking him whether he felt remorse, he declined to respond and pushed his way into his building. (Thus far, his only public apology has apparently been in letters left in his lobby for fellow tenants who suffered through the media circus outside their building.)

To some extent, analysts of criminal behavior say, defining Mr. Madoff is complicated by the wide variety of possible explanations for his scheme: a desire to accumulate vast wealth, a need to dominate others and a need to prove that he was smarter than everyone else. That was shown, they say, in an ability to dupe investors and regulators for years.

Like the former F.B.I. agent Mr. McCrary, Dr. Meloy cautions that he has not met Mr. Madoff and can’t make a clinical diagnosis. Nevertheless, he says individuals with psychopathic personalities tend to strongly believe that they’re special.

“They believe ‘I’m above the law,’ and they believe they cannot be caught,” Mr. Meloy says. “But the Achilles’ heel of the psychopath is his sense of impunity. That is, eventually, what will bring him down.”

He says it makes complete sense that Mr. Madoff would have courted regulators, even if he ran the risk of exposing his own actions by doing so.

“In a scheme like this, it’s very important to keep those who could threaten you very close to you,” Dr. Meloy explains. “You want to develop them as allies and shape how they go about their business and their attitudes toward you.”