Is prayer behind an imam who is later found to be possibly insane valid, and how can the imam's suitability for leading prayer be determined?

One who has reached insanity is not obligated to pray, nor is their prayer valid, nor are they required to make up missed prayers, nor is it permissible to follow them in prayer, due to the absence of their intention. A madman's actions and words are clearly disordered; he neither understands discourse nor comprehends replies, due to the loss of his intellect. The pen is lifted from three: the sleeper until he awakens, the madman until he recovers, and the child until he reaches puberty. So, if it becomes clear that the imam was insane, the follower must repeat the prayer. However, if the imam experiences periods of insanity and lucidity, and one prayed behind him without knowing his state at the time, then there is no need to repeat the prayer. If the man you mentioned has reached a state of insanity or imbecility such that he does not know what he is saying and cannot comprehend the actions and words of prayer, then you must repeat your prayer. But if he has not reached the point of insanity, or if you are unsure of his condition, then the original ruling is that the prayer is valid, and you are not required to repeat it.