A savant who employs this spell is able to note an untruth spoken by a creature, including even a minor evasion of the truth. The material component is the forked tongue of a snake.
The reverse of the spell, evade truth, allows the savant to lie or evade the truth without being discovered by any means. The material component is a pinch of brass dust.
Notes: Restricted to savant-clerics, common. (Updated from Dragon Magazine.)