Usually (and with good reason), mods are not expected to decide if an answer is incorrect. On some sites, though, the mod will take an action if a trusted user raises a flag.
This occurs on occasion on Biology.SE where a user dispenses bad medical advice in comments. The flag is deemed helpful and the comment is removed - presumably because medical advice is OT anyway (though questions still make their way in by not posing it as medical advice.)
Do we need the moderator of a health site - where answers actually deal with issues that impact the health of real people - to step out of the traditional role on occasion?
What can we do about faulty advice if most users don't know it's faulty?
(In one case, the user posted an erroneous answer based on a misunderstanding of the question, and a mod still declined it.)
Edited to add: Is it possible to have a special chat room to draw attention to erroneous answers? Would this be a solution?