According to an American Bar Association FAQ about the grand jury system, "Prosecutors have the right in federal grand juries to introduce hearsay and to otherwise utilize evidence that would not be admissible in a regular trial." The same may (or may not) hold true with regard to grand juries in Kentucky, but even then, I don't know if there is any precedent for the admission of such flimsy "evidence" as polygraph results. It seems doubtful that a grand jury would indict you if the only evidence presented to it would not be admissible at trial. In any event, I think it would be best to retain a competent criminal defense lawyer and not to speak with police again without your lawyer present. If your lawyer can obtain an audio or video recording of your polygraph "test," I would be happy to review it and provide commentary.