Just wondering, in California specifically, can a recording of a conversation by the wife of a husband and wife's conversation within their own home be submitted as evidence if the husband had no awareness of the recording? This is not a personal question, but an episode of "Billions."
In California, all parties to a conversation (people being recorded) have to agree to a recording. There are no special rules pertaining to husbands and wives. It is sufficient that the parties are aware that the recording is being made and they continue to talk, knowing that fact. There are exceptions, under Cal. Penal 633.5, in that surreptitious recordings are allowed in order to gather evidence of "extortion, kidnapping, bribery, any felony involving violence against the person, or a violation of Section 653m". To be used as evidence, there are also "predicate rules" to the effect that you have to prove who the voices are from, that the recording hasn't been altered, and that the recording is reliable (e.g., there isn't a mysterious 18 minute gap).