CA Prob Code Section 4122

If the power of attorney is signed by witnesses, as provided in Section 4121, the following requirements shall be satisfied:

(a)

The witnesses shall be adults.

(b)

The attorney-in-fact may not act as a witness.

(c)

Each witness signing the power of attorney shall witness either the signing of the instrument by the principal or the principal’s acknowledgment of the signature or the power of attorney.