No, a wife cannot just sign her husband's signature, no matter that he is incarcerated. Such such a signature is not legally valid. In fact if a wife attempts to do this, she could be charged with forgery, fraud, and possiblyother offenses - whether not he consented to her doing this.. The correct way for a wife to sign her husband's name is by doing the same thing that anyone who need to sign his signature would do. Namely, get a valid "Power of Attorney" (POA) executed.
A POA is a document that grants an “attorney-in-fact” or “agent” (in this case the wife) to give that individual the legal authority to make decisions for a “principal” (in this case the husband). this individual can be given the authority to deal with only one particular issue (a specific power of attorney) or to handle all or most of the principal’s personal and/or financial matters (a general power of attorney).
Since the laws for creating a power of attorney vary from state-to-state, an attorney should be consulted with on this matter.
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