Legal Question in Wills and Trusts in California

Never heard of such a law. Why would there be such a law? If somebody is of sound mind and signs a will, and ten minutes later they get run over by a bus, why should the will be invalid? If you need to contest, or attempt to invalidate a will, there are plenty of legal avenues including allegations of lack of testamentary capacity or undue influence. Consult an attorney.

If the testator (the individual executing the will) has the legal capacity to execute his or her will, has not been unduly influenced, and the document itself meets the legal requirements under California law, it is a valid will no matter how soon the testator dies afterwards.