California Penal Code
Title 8. Of Crimes Against the Person
Chapter 1. Homicide
A bare fear of the commission of any of the offenses mentioned in subdivisions 2 and 3 of Section 197, to prevent which homicide may be lawfully committed, is not sufficient to justify it. But the circumstances must be sufficient to excite the fears of a reasonable person, and the party killing must have acted under the influence of such fears alone.