Marriage of Jeffries (1991) 228 CA3d 548 is probably the more relevant case.
The best argument is not an argument -- it's proof. Elements:
1. Party X had exclusive use of a community asset;
2. The parties' were separated during party X's term of exclusive use;
3. An expert (forensic accountant) testifies that party X's use had a fair market value of $Y;
4. Expert testifies that party X actually expended $Z in separate property to maintain the community asset;
5. $Y minus $Z is greater than $0.
If all of the above is true, then Party X owes the community $Y minus $Z.
Note: Party X's counterargument is that he is entitled to "Epstein" credits for using separate property to maintain the community asset, and that the separate payments are greater than fair marke value use of the community asset.
Most attorneys/jurists are lousy at math, but if you reduce all of the variables in the accounting, you discover that all the Epstein-Watts/Jefferies c*** still boils down to: community_reimbursement = (fair_market_value_use_of_asset - separate_property_payments_to_cover_community_obligations_for_asset)
Gift issue is simply, "was this really a gift, or was it a payment in lieu of some other obligation?"
Notice issue: California family law actions have all sorts of complex theories of recovery, none of which appear on the face of a petition or response, because many of them arise during the pendency of the dissolution, due to the parties' separation (e.g., Watts, Epstein, Feldman). So, reasonable notice, in the form of a filing with the court, if the issue arises after the mandatory settlement conference, that a litigant intends to seek a credit, reimbursement, sanction allows the judge to consider the issue without an objection or appeal that the defending party did not have reasonable notice.
Ideally, the issues would appear in a mandatory settlement conference or joint statement of issues brief. But, what usuall happens is trial is continued multiple times and somehow, at the last instant, one or both parties starts screaming that they are entiled to this because of that, and the judge will try to prevent either party from raising it, or will continue the trial -- again.
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