Quote Originally Posted by Wraith View Post
As such, they probably have contemporary knowledge of Imperial culture, up to and including employing their own Astropaths and Sanctioned Psykers. The easiest why to find out if someone is a Psyker is just to have another, confirmed Psyker look at them - get a lineup of suspected witches once every ten years or so, have your "Court Magician" look 'em over and send away the ones that are just mutants or otherwise unlucky enough to be picked up by the local PDF/Militia/Whatever.
If I recall (Dark Heresy splatbook, maybe?), this strategy is insane. As it requires the one or two Sanctioned Psykers on the planet to interact with every child born, ever. The Psykers are already way too busy dealing with the internal socio-political structures of the System/Sector to test every. Single. Child. That's why they go with the 'Wait 'til they manifest' approach, because pre-screening every child for Talent is more or less impractical, if not impossible.

Because every child can't be screened this allows rogue Psykers to slip through the cracks, as certain people might have Talents related to hiding or can generate cults of personality, so that the Psyker in question doesn't get reported (or killed) by the citizenry.