I hope I can explain this situation clearly enough to be understood. Mrs A submits a credit card application for herself with her daughter listed as an authorized user. Credit card is issued in the name of Mrs A's deceased husband with daughter listed as an authorized user. Authorized daughter uses credit card and makes credit card payments. Subsequently, authorized daughter receives large amounts of cash through courtesy checks or cash advances. Authorized daughter now denies any knowledge of credit card or responsibility for any incurred credit card debt. The question is: Is the authorized daughter legally responsible for the outstanding credit card debt? Are there any legal ramifications to the authorized daughter's use of the credit card?

Yes, contact the credit card company for any and all signed receipts. Including any advance cash vouchers. If she signed them in her name, then she is responsible. Plus if she is listed as authorized user she may be helod accountable as well as mrs.A for getting the card in her deceased husbands name. That can be construed as fraud because it was done without his knowledge or permission.
Their best bet is to contact an attorney for legal advice.

Yes, she is, if she claims she did not make these charges, she will be required to file a police report for ID theft. And if it turns out she did make them, she will be also guilty of false police report.

Since he was authorised to use the card, and did so by signing the reciepts and the checks.

In addition the mother who applied for the accounts can also be held responsible.

Hmm, don't the credit card companies do a crosscheck for, like in this case, the social security number being used to apply with as possibly deceased?

It is fraud, and both the applicant AND additional cardholder will/should pay for their mistakes.

I am reposting this question because I left out a few facts on the original post that I feel are important to an understanding of the situation.

I hope I can explain this situation clearly enough to be understood. Mrs A submitted a credit card application in 2001 for herself using her own Social Security Number with her daughter listed as an authorized user. Mrs A listed authorized daughter’s home address as the credit card billing address. Mrs A’s husband died in 1999. However, credit card was issued in the name of Mrs A's deceased husband with daughter listed as an authorized user. Only authorized daughter used credit card and made credit card payments. All credit card statements were addressed and mailed to Mrs A’s deceased husband and authorized daughter at authorized daughter’s home address.

Subsequently, authorized daughter received large amounts of cash through credit card courtesy checks. Mrs A died in 2005. Authorized daughter now denies any knowledge whatsoever of credit card or responsibility for any incurred credit card debt. The question is: Is the authorized daughter legally responsible for the outstanding credit card debt? Are there any legal ramifications to the authorized daughter's use of the credit card? Does this situation constitute identity theft and/or credit card fraud?