Legal Question in Business Law in California

Well, embezzlement is a crime, as well as being a civil wrong, which opens up two possible approaches for legal action--involve the police, try to get the D.A. interested in prosecuting, etc., and they may or may not take interest in a full-blown investigation and prosecution. That would be one way. The district attorney (or a grand jury) probably has greater subpoena powers than any private citizen.

Your concept of a civil lawsuit is the other approach; I think instead of embezzlement a civil action would allege conversionand breach of fiduciary duty, and perhaps fraud as well. A civil suit by the innocent shareholder probably should allege the claims both individually for the plaintiff and derivatively on behalf of the corporation -- i.e., a shareholder's derivative suit.

In considering which way to proceed, or maybe both ways at the same time, you have to take into consideration a bunch of factors, including what kind of relief the innocent co-owner and/or the corporation would be awarded, the effect of the suit and/or prosecution on the corporation and personal relationships, costs (you don't have to pay the D.A.), the evidence available, probability of locating the missing funds, and so on.

In a civil lawsuit, soon after the suit is filed and the defendant served, the plaintiff would initiate "discovery" - the statutory process of eliciting information germane to the lawsuit from the other party or parties to the suit and from third parties not named in the suit, such as banks. Nonparty discovery is done by subpoena. Discovery from parties does not require a subpoena; it is merely served on the party or his/her/its attorney. I would start by serving interrogatories on the defendant, asking "where's the dough?" in a dozen different ways. One can also ask the other side to produce documents. This process could either locate the account or narrow the field of banks to be subpoenaed.

I'm pretty sure banks are able to search for accounts based on the account owner's tax ID number, whether it is a SSN or a TIN/EIN. A quick review of privacy laws suggests that banks would be less resistant to releasing information on a corporate account than a personal ("consumer") account due to several laws protecting "consumer" privacy but not applicable to business accounts.