Can person who has signed power of attorney to another, sign a valid will?

snowquail: Wills are legal documents and not at all "wish lists."

Where did the 'forced' signing of this will take place? Were there witnesses? A lawyer? A notary public? This sounds like a melodramatic movie from the 40's... I know when my mom (whose dementia was ramping up) was taken to the lawyer to amend her will, I was asked to leave the room before the actual signing so they could talk to her alone. That was hairy, I was terrified 85 year old mom would start talking about her mom and dad appearing and disappearing in the house! It went well, but we got there just before she went to la-la land permanently.

Snowquail, you are dead wrong about a will being a "wish list." If drafted and executed properly, it is a legally binding document with mandates for distribution post death. Vesting of title is obviously important, but it should dovetail with the will's bequests, if properly drafted.

Wills also address assets beyond real property and financial accounts.

Don't worry about the will. Wills are just "wish lists". What really matters is who's name it on the property title, who's name is on the bank accounts and who's name is listed as the beneficiery.

Yes, please OP, do as 1RareFind says.

It takes a competent person to be able to sign a will.

Let me address your questions from a different angle. You wrote:

" I know a person who was sufering from both parkinsons and alzheimers desease who was practically forced into signing a will by his arrogant son mostly in his and his mothers favour,a year after the person signed a power of attorney over to the mans wife"

What's the source of this information? How did you learn that this person was "practically forced into signing"? I'm sure the son didn't tell you this, so who was the source? If the person has Alzheimer's, and was the source, are you sure it's accurate?

Someone has the cognition to tell you he was "forced" shouldn't have executed the documents in the first place. So you can see that I'm wondering how you learned about this situation, and whether the source was reliable.

Who is "the man's wife"? Is this the wife of the "arrogant son"?

I'm must trying to sort out whether or not the individual about whom you're concerned was manipulated or pressured, whether he understood what he was doing, or not. And, unfortunately, sometimes someone misunderstands the situation, especially when he has Alzheimers.

A diagnosis of dementia does not make someone instantly incompetent, they would have had to demonstrate to the lawyer involved that they understood what they were signing.

One thing I discovered is when you need legal help as much as it's needed these days, it seems like most of the lawyers are only there for the rich. I had this problem when I had a legal issue and I most needed a lawyer but couldn't get one. When I tried legal aid several times, there were no lawyers who were able to help with my situation, and worse yet they said they didn't have the funds to support the case. If you're a one person household with limited money, especially if you're on fixed income, getting legal help is impossible or at least near impossible when you most need it, so be prepared if you happen to be in a limited income situation and if you happen to be a single person household with no outside help

Yes they must have legal capacity to execute the document. Just because they signed a power of attorney does not mean they do not have legal capacity. The only way someone can lose legal capacity is if a court says they do not have capacity. I would hire a Certified Elder Law Attorney right away.

Oh yeah, Do your research about elder abuse because that's exactly what you're describing

You're totally right, a person must be competent in order to make that kind of decision. You need to go to your local human services and find the local APS. You can anonymously report to them exactly what you told us here. Adult protective services is for the patients you're describing. It's illegal to tamper or influence these types of patients. Sadly this is more common than you think, it happens all the time and it makes some people glad they never had kids for this very reason because what you're describing here can happen to any of us.