TWO white-collar criminals received justice in June - Allen Stanford of Stanford International Bank and Rajat Gupta of McKinsey and Goldman Sachs. The actions of one are easy to understand, the other's are extremely hard.

Stanford, a Ponzi schemer who stole $2bn of his eager depositors' money, is easy: if he is not a psychopath, he certainly behaved like one for two decades. Gupta, convicted of fraud and conspiracy for leaking price-sensitive titbits about Goldman to Raj Rajaratnam, the criminally corrupt hedge fund manager who was his confidant and friend, is the puzzle.

Was Gupta always bad, or did he turn bad? Either he fooled McKinsey into electing - and twice re-electing - a fraud as its managing partner or he only later turned into a corporate Narcissus who did not regard himself as needing to obey the usual rules as a board member of Goldman and Procter & Gamble. If he had a moral compass, he lost it.

Psychopathy is "a disorder rooted in lying, manipulation, deceit, egocentricity, callousness and other destructive traits", write Paul Babiak and Robert Hare in Snakes in Suits: When Psychopaths Go to Work. Psychopaths are often charismatic and grandiose, with no compunction about manipulating and exploiting others. "I was the puppet master pulling the strings," one of them happily reminisced.

Stanford had these characteristics in abundance: clever, deceitful, egotistical and manipulative, he bribed regulators and took billions from depositors who were swayed by Bernie Madoff-like promises of high returns. Instead, he lived high on their cash. He is not in the least remorseful, despite being sentenced to 110 years in prison. Instead, in his ridiculous final plea to the judge, he claimed it was everyone else's fault.

Gupta is no psychopath - his crime was far smaller and he lacks Stanford's blind egotism. His sage advice was valued both as a board director and a consultant.

Alan Lafley, the former CE of Procter & Gamble, once compared him to Thomas Aquinas, the philosopher-saint.

The minority view is that he always had suspect traits, although he kept them hidden. "His main objective was to make the senior partners wealthy and he didn't care about the juniors," says one former partner. Gupta clearly has charisma, of the quiet rather than bombastic variety, and used it to ascend smoothly throughout his career. Like politicians, executives who reach the top are not saints; they must build alliances, defeat rivals and be ambitious. They may behave with nobility once in the job but that is not how they got there.

Studies have found that many executives share qualities with psychopaths. One study of British managers identified similar traits in both: manipulative, with superficial charm, grandiosity and a lack of empathy. These flaws, far from holding them back, helped them rise.

Of course, sharing traits does not mean that all managers actually are psychopaths. If that were so, many of us would fall into the spectrum.

Few CEOs are as coldly heartless as Stanford. But I am struck by Babiak and Hare's description of sociopathy, which is not a mental illness: "Sociopaths may have a well-developed sense of conscience and a normal capacity for empathy, guilt and loyalty, but their sense of right and wrong is based on the norms and expectations of their subculture or their group. "

That sounds distinctly like Gupta, who became part of Rajaratnam's circle and, as one prosecutor put it, "launches right into a detailed discussion of what happened at a Goldman board meeting in St Petersburg as if he's talking about what happened at a Yankees game".

He was also taped calmly talking about Rajaratnam paying Anil Kumar, a McKinsey partner, $1m a year for information. Did it slip his mind that he once ran the place, or did he always approve of partners taking bribes?

The nastiest conclusion is that the "norms and expectations" of the corporate elite are corrupt - that at such heights, illegal information-sharing is no big deal. I hope this is not the puzzle's answer.

© 2012 The Financial Times Limited

TITLE: Snakes in Suits: When Psychopaths Go to Work

AUTHOR: Paul Babiak and Robert D Hare

PUBLISHER: Harper