Andrew D Atkin:

It is estimated that 0.5% of woman and 2% of men are psychopaths.
Take a look at America. They're zapping people with (arguably) dangerous scanners at airports because a given passenger might be a threat to the public. Fair enough? Maybe. But going by history, statistics and still our present, we must admit that the most profound public threat is and has been governments - not individuals or isolated groups of individuals. Governments are where the most incredible and vast acts of terrorism have typically come from.
So where are the controls to protect the public from the threat of the wrong hands acquiring great power? Where are those "political scanners" for the public interest, and who can argue that it does not make sense to employ them?
Well, it looks like we now have the tools to clinically recognise psychopaths, whether those psychopaths want to be recognised or not. Modern research using advanced brain scans has shown that there are distinct differences between a psychopaths brain and a normals. But first let's review what a psychopath actually is:
What is a psychopath?
The type of psychopaths that we should be focusing on are corporate psychopaths, as they have been termed. These are people who do not care about others to a "reptilian" extreme, are fake, manipulative, diabolically self-serving, but are people who do not tend to end up in prison due to their intelligence and self-control.
Corporate psychopaths can actually be worse than the types you will find in prison because they are particularly good at obtaining power; and, eventually, being highly destructive from their positions of power.
The characteristics I highlighted have been directly correlated to distinct differences within the function and structure of the brain. Psychopathy runs way deeper than just an imperfect upbringing. It has a genetic base, and probably a major epigenetic base (epigenetic = genetic 'switching' via the womb environment).
This is why psychopathy is basically incurable. The damage is just far too primary for existing therapies to reach. When someone's neurophysiology makes it truly impossible for them to care about others there is only so much you can (and can't) do. A psychopath couldn't care even if he wanted to. Again, that is how deep-set the damage is.
As I personally see it, psychopathy is a kind of socio-emotional autism. The psychopath experiences no emotional meaning in being a "part of" and "with" other people. Indeed, findings have suggested that their mirror neurons are dysfunctional. Mirror neurons are an essential part of our capacity to understand and relate to others on an interpersonal level.
The following is a great little documentary "I, Psychopath" which can give the reader a feel for what a corporate psychopath can be like:
Why are corporate psychopaths good at obtaining power?
Because they're living in a chess game might be a good answer. Psychopaths are happy to do whatever they can to win. They are the personification of ruthlessness. They can also be very cunning as they can (and do) naturally think of strategies that normals would never consider (due to morality). So the psychopath sees and exploits more opportunity.
In a competitive world the intelligent psychopath can be extremely competitive. That is the problem. Remember it's hard to win an election by telling people the truth. The psychopath can warmly lie to your face, much too easily.
Screening? Yes!
The USA's political system was built in a manner specifically to protect against corruption. The founders were realistic about the fact that the highest of places tend to attract the lowest of people, so they created a governmental organisation based on the separation of powers*.
This is the kind of thinking we need today. We need to stop wasting time throwing eggs at rotten politicians, and instead create controls to stop them from becoming politicians in the first place.
Sophisticated psychological profiling moves in this direction. We need to make it uncompetitive to be a psychopath, and luckily now we can. All prospective politicians should be expected to go through psychological testing, and their profiles should be made public via the Internet. Yes, this is intrusive somewhat, but it's a price that they should be expected to pay considering the importance of their positions.
Psychological testing for teachers and fireman has already been introduced in some parts of the world. See here for an excellent article on this.
Not just politicians?
Personally I do not think that New Zealand's political scene is overrun with psychopaths. Speaking intuitively, I think you would be more inclined to find them hidden away in your bureaucracies.
I believe that psychopathic testing should be applied to powerful public servants, and it should be applied to powerful players in the private sector as well. Basically, once an individuals official influence reaches a certain substantial level, they should have to accept open psychological testing.
Conclusion:
Though psychopathy is a particularly nasty problem, it is certainly not the only one. There are also the problems of zealotry and group-think - more "normal" problems that virtually all of us suffer from to given degrees.
If we can somehow screen for other concerns for a more complete profile, then that would be a good idea too. But again, psychopathy is a particularly dangerous attribute that we should definitely go out of our way to look for, using compulsory testing.
27-6-11: An involved letter was sent to me responding to this post. I gave it a dedicated post here.
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*Unfortunately it seems to be breaking down today because those 'separate' powers are getting ever more infiltrated by the same corrupt interests. So the separation is becoming cosmetic, so to speak.
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Addition: 21-2-11:
Tyrants:
Imagine walking up to a new born baby and shooting it in the head, in front of the mother, and just to let everyone know who's boss. Obviously this unimaginable vulgarity takes either pure psychopathy or extreme insanity. But it's the sort of thing that goes on where psychopathic dictators have been in charge.
Psychopaths are everywhere, but usually we don't get to see them acting-out North Korea style. But that is only because psychopaths need power to be visible. The successful psychopath is not self-destructive.
In our society we have created intensely strong behavioural social pressures that allow us to live in the illusion of our "civil society". It's a dangerous illusion, because we can (and do) start to believe in the fairytale that everyone is such a lovely person...because we don't get to see what that "lovely person" is doing to their children, in their own home. That is, we don't get to see them when they have the opportunity to be the tyrants that they might very well be.
If you give someone the opportunity to treat an entire nation like they do their children, then they will do it. They will do it because scaling up the game does not change it - they are the same subjective psychology, living in the same psychological world. Power only exposes corruption - it does not create it.
Again, the tyrannical parent who ruthlessly rules over his 4 children with that absolute feeling of entitlement will do just the same to 4 million, if given the chance.
You can see my point. It is more than important to create controls to block psychopaths from positions of serious power. The latency for tyranny is just too real and prevalent. Even if we can't see it directly it is everywhere. Go by the child abuse statistics.