The critical item in a series of similar but neutral items used in Peak of Tension (POT) tests. In a known solution POT, the key is the relevant question that contains the incriminating information that only a guilty person should know. A key in a searching POT is the test item that holds information that only the guilty person knows and the PDD examiner is trying to uncover. In stimulation tests, the key is the question to which the examiner directs the examinee to lie. Also See: false key.