This is felony credit card abuse. You can absolutely go to jail for it. You would stay in jail until someone posted your bond. If you were not bonded out, you would stay in jail until you entered a plea bargain agreement for probation (if you pled to prison time obviously you would not be released) or until you had a trial (if you were acquitted or placed on probation I'd convicted). Repaying the money would be a condition of probation, in addition to fines and court costs, monthly probation fees, and any other costs of probation. If a case is filed against you, you will need an experienced attorney working for you immediately.
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Sure, you can go to jail. In fact, if your in-laws want to get out of the debt (and they certainly should) they will most likely have to provide a full explanation of what happened (and who did it) to the credit card issuer. The issuer, for that amount of money, will likely pursue it further, I'd suggest a discussion with a good criminal lawyer today. I changed your topic to criminal law as it is not a bankruptcy question.
Yes, you could go to jail. Moreover, your debt is probably not dischargeable in bankruptcy. Your excuse ("we were going through a rough time") is not much different than the one people use who rob convenience stores. See a criminal defense attorney, and stop blabbing about this online because you may waive your 5th amendment privilege. (In fact, you probably already have.)
Answers on Avvo are for general information purposes only and should not be relied upon as legal advice. No attorney / client relationship is created by providing this answer. For specific advice about your situation, you should consult a competent attorney of your choosing.