The law about capacity and execution of wills gets down to fine details in state case law so you need to check with a Kansas lawyer. That issue about the signing may be covered in case law or perhaps not.
However, in general, capacity requires a few simple things at the very moment of signing and publication of the will: knowlege of the natural objects of one's bounty (ie family members), knowledge of the nature and extent of one's property (not every detail just a good idea of what one has), understanding and intending the specific contents of the will, and an understanding of the signficance of signing a will (ie that it disposes of property after one dies).
The key thing that people often dont understand is that to overturn what appears to be a validly signed will, you need evidence of incapacity at the moment it was signed. Now day in and day out, people with ailments affecting cognition are signing wills and if they have a good idea of those factors above at the moment they sign the wills it is usually good enough. I have read a case that says neither the fact someone is an alcoholic nor on pain medication in general are not proof of incapacity at the very moment of signing. So oftentimes I have to inform folks with issues such as you describe that a person who has mental illness or who may be on various types of drugs is not proof in itself of legal incapacity at the pertinent moment in time.
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You need to consult a KS lawyer if you want specific answers.
Legal disclaimer: This answer does not constitute legal advice. I am admitted to practice law in the State of Missouri only, and make no attempt to opine on matters of law that are not relevant to Missouri. This answer is based on general principles of law that may or may not relate to your specific situation, and is for promotional purposes only. You should never rely on this answer alone and nothing in these communications creates an attorney-client relationship. less