Legal Question in Wills and Trusts in California

Your question makes no sense. A "Durable Power of Attorney" is a set of legal rights and responsibilities that is reflected in a written piece of paper. It can no more sign a court document than a rock can sign a court document. And who has to sign a court document depends on the document and the rights and powers of the parties to the court proceeding. You are also having problems using pronouns which are almost always confusing. Let me give you some proper terminology and maybe you can craft a question that can be answered. The person to whom a power of attorney is given is called the "attorney in fact." The person who gives the power of attorney is called the "grantor," short for "grantor of the power." Also, "the court document" tells us nothing. You need to tell us what is being signed for what purpose.

wish there was a "like" button for Mr. McCormick's reply!

The attorney in fact cannot give himself power of attorney without the grantor signing the document giving him or her the power.