I have 2 bank cashiers checks from 2002 made payable to a deceadent whose estate I am executor of. Cash them?

You can contact whoever the issuer was and request to have them write a new check. However you will probably need to take them to court. Was the person the checks were written to unable to cash them for some reason, or did they just choose not to? If there was a medical or mental incapacity they were dealing with that made them unable to cash the checks you would probably have a better case than if they just chose not to do it before the expiration date.