Years ago, I was involved in a filthy divorce where I represented Mom and she ran out of money. We couldn't hire a forensic accountant to trace money (usually only worth the $ for issues re business income or separating out separate property, anyway).
We subpoenaed all Dad's bank accounts for the last two years.
We, then, calculated all of Dad's deposits and all of Dad's payments, and reconstructed his income/financial picture from that. It wound up with a very successful outcome for Mom.
It was tedious, and the banks charged quite a bit (we subpoenaed about ten banks, some charged a research fee, even though the accounts were closed a long time). Mom saved money by having her friend deliver the subpoenaes and she did most of the listing of deposits.
In your case, if his wife is working, then it would be hard to reconstruct only his income from his checking accounts (he may also be depositing money in savings or company IRAs - Sears may not be helping him hide income, maybe he's dumping large amounts into a company deferred compensation/IRA account)
You could do interrogs to find out where he banks, then do subpoenaes.
If you send subpoenas to his banks, be careful to ask for any account information using his name, birthday, and social security number, to include account # xxx(known), and any other account.
Be aware that the bank will charge you to respond to the subpoena, but, at least you, hopefully, are getting at his actual money information. If you do this, examine the accounts for transfers to, or from, other accounts & look at what he's spending money on.
If you're in CA, the subpoena can be issued by an attorney - as long as there is a current case before the court.
