Is a wife responsible to pay her husbands courts costs/fines/restitution in California?

If you say "incur after marriage" then it would have to be about about a crime to be committed after marriage. If it is to be imposed after marriage then the crime occurred before marriage but the sentencing will occur after the marriage. In either case marriage with someone who will either be committing a crime or has done so but has not yet been sentenced does not sound like a good idea. A prenuptial agreement will keep your future income as separate (not community) property and will clarify that what you already have will not become community property unintentionally or that he could allege you gave him all your property upon marriage. You must still keep everything separate. That does not mean that people whom your future husband might owe money or damages will not sue you. It just means you might be protected from having to pay but might have to spend money defending yourself in court. You really need to discuss everything with a family law attorney to whom you can explain the your concerns, reason for the marriage and give information about your assets and income, etc.