California Code, Probate Code - PROB § 12401

In proceedings under this part, a person who has not been seen or heard from for a continuous period of five years by those who are likely to have seen or heard from that person, and whose absence is not satisfactorily explained after diligent search or inquiry, is presumed to be dead. The person's death is presumed to have occurred at the end of the period unless there is sufficient evidence to establish that death occurred earlier.