Monsters always get the headlines.

Whether Clifford Olson, Paul Bernardo or Josef Fritzl, the Austrian recently discovered to have locked up his own daughter as a sex slave for more than two decades, those who commit horrifying crimes often get endless, expansive coverage by the news media.

The public is repulsed yet fascinated. "How could they?" we cry, judging their criminal behaviour through our own internal filter of right and wrong, of empathy, emotion and justice - in other words, our conscience. All too often, it seems, no answer - at least none we can truly understand at gut level - emerges.

Then again, could an average "normal" person ever truly understand a psychopath? Would they even want to?

Psychopathy has become the recognized field of scientific study of those individuals who, for want of a better definition, are missing a component shared by literally 99 per cent of humanity - a conscience. Research has shown psychopaths feel no guilt over their actions; in fact, they're physiologically unable to. They can be taught right from wrong, but that inner voice which reminds us which is which remains indifferent, in their cases, to their choices.

That's the dry explanation. Now, take this self-test. Recall any recent decision you've made that involved, in some way, a choice of conscience. Perhaps you promised somebody something. Maybe you had a chance to take advantage of a situation. Whatever. Now, try to imagine making the same decision, but without concern for right or wrong, guilt or shame. Imagine, if you can, that those hardwired considerations simply weren't there at all. Can you do it? Even if you can mentally make the wrong choice, can you do it while suppressing your internal moral meter? Can you do the wrong thing and truly feel guiltless?

Olson and Bernardo, of course, are infamous criminal psychopaths. For their unconscionable crimes of sexually assaulting and murdering children and young women, both are thankfully now in maximum security prisons in Canada, from which they'll likely never be released.

No one has officially labelled Fritzl a psychopath yet, but it seems to me that he is one, based on what's been reported. What other than an absence of conscience can explain how a father could imprison his 18-year-old daughter in his cellar/dungeon for 24 years, raping her repeatedly, while lying to his wife - upstairs, apparently unaware - about their missing child's whereabouts? (He told his wife their daughter had run away with a religious cult.) Fritzl has reportedly said he feels no remorse - another trait of the psychopath, say experts - while his lawyer has declared he'll try to get him declared insane.

Until this all came out, of course, no one thought Fritzl insane. He was feared by those close to him as a man who brooked no dissent. Others, though, described him as an "affable" man. That presentation of dual personalities, says Stephen Porter, a psychopathy expert at Dalhousie University, is common among intelligent psychopaths. Porter, who believes the Fritzl case has "all the hallmarks" of psychopathy, says psychopaths aren't insane - they know what is going on and what they're doing - but have a "pathological disorder." They're often quite adept at fitting into society, mimicking emotions, acting "normally." Inside, however, they're merely playing a game they've learned, one that keeps their true nature hidden.

Now, consider this. Experts estimate perhaps up to one per cent of the population has psychopathic tendencies. In a country the size of Canada, that's 300,000 people; in Nova Scotia, around 9,000; in Halifax and environs, more than 4,000.

And though psychopaths make up a disproportionate amount of violent criminals, Canadian Robert Hare, the world's foremost expert on psychopaths (and author of Without Conscience: The Disturbing World of Psychopaths Among Us), tells us that most psychopaths don't become criminals at all.

Yet they're still out there. Many are said to be drawn to jobs where lack of conscience can be, or at least seem to be, an advantage. Think of careers where getting ahead is too often accomplished through ruthlessly lying, backstabbing and trampling all those who stand in your way to the top. You can imagine, as well, the emotional carnage that non-criminal psychopaths could leave in their wake in personal relationships.

Here's something else about psychopaths. Experts say no treatment program ever tried has worked on psychopaths. Such programs, in fact, instead often made them more likely to reoffend. As Dalhousie's Porter put it, psychopaths don't even believe they have a problem. To them, it's the rest of the world that's screwed up.