Fight the Power Word, Kill

From Warhammer Fantasy Roleplay 1st edition (1986):

"Observation
Characters might enter a room and see the rough stone walls, the upturned chair, and the heavy table. But would they be likely to see the scratches on the floor made by the secret door or the dark smear of blood on the chair?

"If a character searches these areas, the scratches and blood will be found automatically, because they are not hidden. However, the gamesmaster can give players a chance of their character just noticing these features, even without conducting a proper search.

"Roll secretly against the character's I as soon as there would be an opportunity for the character to cast a cursory glance over the room. A successful test reveals a single clue, where present. Success by 10% or more points reveals additional clues at the rate of 1 clue per full 10% of success, until the character has noticed everything there is to see.

"Characters cannot use observation to uncover hidden items. Hidden items can only be uncovered by a deliberate search."