Can a person diagnosed with dementia still have the capacity to make decisions?

Another twist of a person with dementia and decision making: You could ask the same question to them at intervals of 5- 10 minutes apart. You may get a different answer at different times...... very inconsistant.

So true. We are having the same issues with mom. She can't work the appliances, doesn't bathe at all, is paranoid, hooked on laxatives, gets people mixed up, can't remember what was said or what she did 5 minutes ago, cannot be trusted to take meds, lies, accuses people of stealing, etc. That being said, she can carry on a conversation about generalities with ease and could, in the short term fool someone into thinking she is capable of making a legal decision. (even though she can't remember who a relative is or their relationship or even if she ate 5 minutes ago) That's what makes it so difficult because dementia is not always an all or nothing situation and doctors are so hesitant to make the determination a person is incompetent. Mom definitely is, but given a situation where she had the chance to stand up and answer questions a judge asked, she could probably pull it off.

I agree with evaluation by expert. I would like to add that I have noticed a fluctuation in capacity, as others may have also, which can allow the person to convince a lawyer they are in control of their facilities during a conversation. Thus the evaluation by the expert is critical. My mother is in advanced dementia, but still capable of giving good advice on how to handle life situations to us when actively engaged in a conversation about the situation.

A person examined by a neuro/psychologist and had a 3 hour extensive evaluation to diagnose the dementia and its stage, is the best person to evaluate competency. These docs are the experts. Often people with dementia seem competent to family and health professionals, when they are really incompetent to make decisions.
This is why these evaluations are crucial to decision making, whether medical or legal.

Strange & tricky question I must say.It's funny you asked that question.Because,I wonder the same thing?
A question to your question is,(Does dementia automatically mean your incompatent?)Compatent or incompetent is the main question?
Personally.I feel the word dementia ,it's a big legal scam for attorneys.
I was told that if a person has dementia no attorney will risk losing their bar to change or create a document.But,I learned that statement is incorrect.Because,many attorneys do take the risk.Elderly people with dementia is prey for attorneys.Attorneys seek peolpe that is incompatent to take advantage of them.All attorneys see is Money.If there's money to be made attorneys will do it.Money talks!
There's many cases of the word dementia.Some dementia is worse then other.
But,the factor remains this,compatent or incompatent?I'm no attorney or doctor.
But,I feel that if a person has dementia and is taking pills for dementia?That's incompatent!...If a person can't remember signing a document that becomes a problem.Requires coaching the person to do so and that is what attorneys do with dementia.

Yes.

"Dementia" covers a huge range of cognitive impairments. Some people with dementia cannot even safely decide what to eat, or they might have toothpaste for breakfast. Others can decide on what they want in their wills and who they want for POA.

Someone whom the courts have deemed incompetent cannot enter into legal contracts, but not all persons with dementia are legally incompetent.