If someone is diagnosed with Alzheimers and they are made to sign power of attorney over to another person but they dont remember it is it legal?

I am sorry to hear about your father's condition. As for your question, it can be legal for a person with a dementia or Alzheimer's diagnosis to sign a power of attorney, and the resulting power of attorney can be perfectly valid. So much depends on the actual facts and circumstances that it would not be possible for anyone in this forum to tell you whether the power of attorney your father signed is actually valid, or whether he signed it of his own free Will. In order to sign a power of attorney ("POA") in Georgia, the person who is signing it (the 'Principal"), needs to understand, at the time he signs, what he is signing and what the document does. This requires a relatively high degree of cognitive capacity; however, it is possible that someone could have a dementia diagnosis and still be competent to sign a POA for a while after receiving that diagnosis. It is also possible that someone could have the required degree of capacity to sign a POA at the time the POA was signed, and to have signed it voluntarily, but to later forget what he did and why. In order to know whether the POA your father signed was valid, and whether he signed it willingly or whether your mother was effectively forcing him to sign something he did not want to sign, I would generally need to have met your father at the time he signed the POA and to have more knowledge about his mental state. Hopefully, your mother and he went to an experienced, ethical estate planning or elder law attorney, and that attorney met with your father, determined that he was likely competent to sign the POA and was doing it of his own free will, and then prepared it and helped him sign it. That said, if you think that it is unlikely that your father could have been competent to sign the POA at the time he signed it, or if you think that your mother is abusing him financially or otherwise misusing the POA (even if it was valid when it was signed), then you may want to consult an elder law attorney who specializes in guardianships and conservatorships, especially contested ones. The attorney can then learn more from you about the whole situation and give you advice on what steps, if any, you may be able to take to help make sure that your father is being properly cared for.

An Alzheimer's diagnosis by itself does not show that the person lacks legal apacity to sign either a Durable [Financial] Power of Attorney or a Medical Power of Attorney.  People are regularly advised to get these documents immediately upon receiving the diagnosis, before the disease progresses to the point that they lack legal capacity to do so.  That they may not recall signing them later is a feature of the disease and says nothing about their legal capacity on the date of signing.