Polygraph tests are so unreliabe that the results are not allowed in court as evidence unless all the affected parties agree to that evidence being submitted.
You should stop talking to cops including the DA. None of these people have your interest at heart. You are accused and they want you to talk to them because they tend to believe the accusation. GET AN ATTORNEY AND SHUT UP!!!!!!.
The above is not intended as legal advice. The response does not constitute the creation of an attorney client relationship as this forum does not provide for a confidential communication.