Question and background:
My mother died. We live in New Jersey. Is my father responsible for her credit card debt? The accounts were in her name only.
I'm very sorry about your mother...wishing you and your father peace and comfort in this time of loss.
The following comments are shared as information and not legal advice. I encourage you to consult an attorney who practices in New Jersey for any advice specific to your situation.
Spousal responsibility for debts generally depends on who signed the debt contract, whether the state they live in (or lived in) is a community property state, and whether the debts were accumulated during or previous to the marriage.
If your father never signed the original credit card agreement, then typically he would have no responsibility for your mother's credit card debt.
New Jersey is not a community property state. So your father would typically have no responsibility for the "community debts" (debts of the couple), just those that he signed for. The exception might be if your father and mother previously lived in a community property state and the credit card agreement was originally signed and/or debts accumulated by your mother while living in that state. Community property states include: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin.
So given what you indicated in your question, it's unlikely that your father is responsible for your mother's credit card debt. However, your mother's estate is still responsible.
When someone dies, their estate must pay their outstanding debts. So if there are assets in your mother's estate, the assets may have to be sold to pay her credit card debt. If her credit card debt exceeds her assets, presumably the estate could pay as much as is available and then the lender would likely write-off the remainder.
Again, this is not legal advice, so use this general information as a starting point to know what issues to further investigate.
Hope that helps. Take care.