[roel_v]

You make it seem as if lie detectors somewhat work, except that they have a stochastic failure rate of x%. They don't, they're snake oil. Whole libraries have been written about it, one can start at https://en.wikipedia.org/wiki/Polygraph and follow the literature from there. No civilized country allows lie detectors to be used for any 'real' purposes except the US.

So no, it's not a worthwhile tradeoff, because it's hardly better than rolling dice.