d. Undue Influence
There are three ways of establishing undue influence.
At common law, to make a prima facie case for undue influence, the claimant must show (1) the testator has a weakness that made him susceptible, (2) the wrongdoer had access to the testator, (3) it is the wrongful act that got the gift, and (4) an unnatural result. Where the plaintiff prevails, only that portion of the will affected by undue influence is invalid. That part goes to the residuary, the heirs by intestate succession, or by constructive trust.
In the alternative, a claimant may establish undue influence by the use of a presumption. Under California law, a presumption of undue influence arises when (1) a confidential relationship exists between the testator and the wrongdoer, (2) the wrongful act got the give, and (3) an unnatural result. The consequences here are the same as the common law test.
Finally, a claimant may rely on statutory undue influence. California generally invalidates a donative transfer from the testator to (1) a person who drafted the instrument, (2) a person in a close relationship with the drafter, or (3) a person who is in a fiduciary relationship with the testator. However, these rules do not apply if the testator is related to, married to, or co-habitats with the drafter or if the instrument is reviewed by an independent attorney who counsels the testator. Upon a finding of statutory undue influence, the devisee does not take the gift, but only to the extent that the gift exceeds that person’s intestate share. http://www.law.stanford.edu/sites/d...ningps.doc