Who must take an oath to verify the identity of the Principle?
The notary administers oaths but does not take an oath to verify anyone's identity.
The principal is absent and cannot take an oath before the notary.
A credible witness identifies someone to the notary; the subscribing witness is the one who takes the oath in a proof of execution.
The subscribing witness takes an oath before the notary, swearing to the identity of the absent principal under CC §1195.
Explanation
In a Proof of Execution by Subscribing Witness, the subscribing witness must take an oath to verify the identity of the principal who signed the document but cannot appear before the notary.