As a side note, there are ways for an evil character to hide their nature from the "detect evil" ability. And yes, those ways involve magic.
NOTE: The D&D 3.5 edition 3rd level clerical spell Undetectable Alignment (Conceals alignment for 24 hours) would do the trick. I am sure that those evil folks aligned with Corath can have that cast on them almost every day
OK well for starters, a Paladin's Detect Evil ability is not an NWN thing, but a d20/D&D thing, which probably explains its absence from LORE.
Given what I linked and given that telepathy, psychic abilities and the like aren't available to PCs and 99.9999999% of anything you might encounter, detecting intent is akin to mind reading.
The real question is, why does Detect Evil need to be GM adjudicated?