What is the process to declare a person incompetent?

The proceeding you need to initiate is a guardianship not and incomepetency proceeding. Your grandfather appears to be in need of help and the guardianship proceeding is the appropraite way to proceed. This office has handled many such proceedings on Long Island. The proceeding is filed in the Supreme Court in the County where your grandfather is presently located. You tell the Court in the petition what problems your grandfather has and waht needs to be done; once the papers are filed, the Court appoints an independent person called a Court Evaluator to investigate and report back to the Court as to the matter; then the Judge holds a  hearing and takes testimony - where your gradrfather is to appear; if he cannot appera the Judge generally travels to the location where he is located, unless his personal apperance at the hearing would not accomplish anyhting, ie, the person is comatose and cannot respond to questions, etc. The Judges usually prefer a family member to be the guardian of that individual. Another step is to have the local county Adult Portective Services Unit investigate the matter to make sure your grandafther is not being abused. If there is anything further required please contact this office. Good luck