If John has power of attorney for Sue, can he swear under Oath for Sue? No, he can’t. But, he can sign documents on Sue’s behalf.

To sum it up, he can swear at Sue, for not swear for Sue.

This is an issue doing loan signings involving Powers of Attorney. Most of these signings have Affidavits that need to be sworn to. So, the agent swears to them. And that is that.