Must you notarize the POA of an incompetent person?

A Power of Attorney is customarily notarized.

However, the bigger question is the validity of a Power of Attorney that is executed by an incompetent person. In general, it is not valid, as the person does not have the capacity to grant the powers to another. Therefore, if there is reason to execute a Power of Attorney (such as, in anticipation of potentially dangerous surgery), it should be done prior to the event that could lead to incompetence.