Just because you got away with shooting your first wife in the head while she slept doesn't mean that you're going to get away with shooting your third wife in the head while she sleeps. Yeah, the San Bernadino police might have been convinced that the first killing was an accident. But when your wives keep getting shot in the head -- well, eventually we're going to get a wee bit suspicious about the resulting coincidence. Even here in San Diego. At which point we'll convict you for both the first murder (in 1973) as well as the second murder (in 2004). And the Court of Appeal will affirm.
Lessons of the day: (1) Don't shoot your spouse in the head; (2) Don't do it again.