In California, a printed Will (that is any will that comes out of a printer) must be signed by the person creating it, and by two witnesses. If the Will is not signed by two witnesses, then it is invalid. Many people think they can have the Will notarized, but notarization does nothing to validate a Will. Only two witnesses are allowed, and required, to create a valid Will.
What happens if one of the two witnesses to a Will is also listed as a beneficiary under the Will terms? Is the Will still valid? When a person is both receiving a gift under the Will, and also acting as a witness to the Will, we call that an “interested witness.” They are “interested” in the sense that they receive some interest in the estate under the Will terms. California Probate Code assumes that an interested witness has a strong incentive to act impartially. In other words, they would not make a good witness.
So BE WARNED: To paraphrase California Probate Code section 6112, when an interested witness signs a Will there is a presumption that the gift to the interested witness was made under “duress, menace, fraud, or undue influence.” Because of this presumption, the gift to the interested witness is CANCELLED. However, the Will and all of its other provisions are still valid.
The interested witness can try to overcome this presumption, but that can be hard to do. This presumption would not apply if two other non-interested witnesses signed the Will. In other words, if the Will was witnessed by three people—one interested witness, and two non-interested witnesses—then the presumption of undue influence does not apply and the beneficiary who is also a witness would be entitled to their gift.
The bottom line: a beneficiary witness will not invalidate the Will, it only invalidates the gift to the beneficiary witness. Seem fair? That depends on who the other Will beneficiaries are.