Lie detector tests - for who?

So lie detectors are to be introduced for benefit claimants.

Well what's good for the goose is good for the gander. So why not subject party leaders to lie detection tests regarding their manifestos before General Elections? And better still why not bring out the tests for a forensic cross examination of the members of the government who launched the Iraq War? An come to that why not test those who voted for war as to whether they truly believed in it or whether they voted in the interests of their careers?

Or are lie detector tests only for the little people?