It depends. If the additional cardholder is designated ONLY as an authorized user, that is - that person's credit history was not used together with the decedent's credit history for the original credit line - then no, because the credit line is linked only to one social security number. If the additional cardholder applied as a co-applicant (not added as an authorized user) with the decedent for the original credit line - then more than likely, yes. Individual state laws take precedence. Ask for an original copy of the contract from the creditor to be sure.
It sounds as if you're not legally responsible for the deceased client.
The probate code would explain the process for closing an estate.
death
No one. In that case the debters are SOL (although I believe they may be able to seize the deceased persons assets and sell them all to pay off as much of the debt as possible)
Wake them up and ask them!
No, DNA can be taken from deceased persons.
Marriage is a contract. A deceased person does not have the legal capacity to willingly enter into any contracts.
yes the funeral home usually does a deceased persons nails,and hair and general grooming to get them ready for their "showing"
no
Your local police department
If they have the letter of authority, yes.
Not unless they were guarantors of the debt.