A physician's declaration of incapacity is useful as evidence to defend or enforce a durable power of attorney. However, only a court can make the final legal determination of mental capacity to make personal decisions.

If your siblings manage to get your mother to execute a new durable power of attorney and thereby revoke yours, then you will have to petition the court to either have the new power of attorney revoked, or request a formal conservatorship hearing so as to have yourself appointed conservator and thereby void all of the previous powers of attorney.

Probate Code 4540-4545 (POAs) 1800 and continuing (conservatorship).

For a probate or elder law attorney referral, see: http://www.abanet.org/legalservices/lris/directory/main.cfm?id=CA and www.martindale.com.

Hope this helps.

Terms and Conditions: By your continuing in this conversation with me, or by your clicking “Accept”, you are expressly agreeing to all of the following: (1) our communication is for entertainment purposes only; (2) you are not consulting me in my professional capacity as an attorney; (3) you do not seek to establish an attorney-client relationship with me, nor do I with you; (4) you will not rely on anything I say and you will obtain appropriate legal counsel via a traditional/office consultation with an attorney licensed to practice in the jurisdiction where your legal issue arises (and you may not use our communication to avoid taxpayer penalties imposed by the U.S. Dept. of Treasury); (5) by communicating with me in this public forum you are irrevocably waiving any right to privacy, confidentiality and attorney-client privilege concerning the matters discussed. You further separately declare that any payment made by you is not consideration for this contract, nor offered for any services rendered by me on your behalf, but rather is made in genuine admiration and respect for my desire to help others. If you do not agree with these terms and conditions, then you must advise me immediately.

A physician is not a judge. The physician's declaration is merely evidence of an expert opinion about a patient's mental capacity. The physician's opinion has no final binding legal authority (except in situations where a person is temporarily held in a psychiatric facility for observation).

Your POA is valid until it is revoked by the creation of a subsequent POA. Similarly, the POA can be confirmed by the court, as can the grantor's legal capacity. I'm merely warning you that it's quite common for battling siblings to find a notary public to certify a person's signature on a subsequent POA, and thereby void a prior POA, and that the only legal means of stopping the nonsense is to petition the court for a conservatorship.

Note: you can also contact county adult protective services and request an investigation. However, if the county decides that your mother requires assistance and that the relatives are engaged in her manipulation, then the county will petition the court for a public guardianship, and a third-party neutral may be appointed to control the conservatee's estate -- which means that all family members will be out of the loop.

But, that's an option that you can take, if you don't want to pay for a lawyer to help you obtain a conservatorship.