Can a convicted felon get power of attorney over someone in the state of Alabama?

My uncle is a convicted felon from the state of Alabama. He embezzled money from a bank that he worked at and he went to prison for two years. Now that my grandmother (his mother) is losing her mind (she has Dementia) he took advantage of her and got Power of Attorney over her. He also had the papers back dated, she also said that she does not remember signing any papers. Can he legally do that?