Q: Dear Sage,
If a trap needs an attack roll to hit, is the attack against your normal AC or flat-footed AC?
A: Technically speaking, any attack made against you before you’ve taken your first action in combat, or any attack made by an attacker you can’t see, uses your flat-footed AC. Most trap attacks fall into one or both of those categories, and thus by a strict reading of the rules should treat their target as flat-footed.
Of course, any trap that doesn’t fall into either of those categories would use your normal AC. A wall scythe trap that activates every round of combat wouldn’t treat its targets as flat-footed once they’d taken an action.
About the Author
The Sage is a mammal classified in the bear family, Ursidae, native to central and southern China. Debate continues as to whether he is truly a bear or more related to the raccoon rather than the bear, or perhaps in a family of his own. When not eating bamboo and answering rules questions, he works under the nom de plume of Andy Collins as an RPG developer in Wizards of the Coast R&D, where his development credits include Complete Mage, Dragon Magic, and the Player's Handbook v.3.5. He can be easily recognized by his large, distinctive black patches around the eyes, ears and on his rotund body.