PDD outcome where testing was completed, but neither deception nor truthfulness can be diagnosed because the physiological data are inconsistent, inadequate, artifacted, or contaminated. There is disagreement whether an inconclusive outcome should be considered an error when computing validity of PDD. Some argue that examinees are either truthful or deceptive, but never inconclusive; therefore, such an outcome is necessarily in error. Conversely, in the forensic sciences it has been asserted that the inconclusive outcome is used to assess utility, but not validity, because samples in forensic disciplines are often inadequate, or contaminated. Because of this controversy, PDD validity studies report accuracies both with and without inconclusive results. In practice, inconclusive outcomes are the default results when the criteria for deception or not-deception decisions are not satisfied and are a matter of the decision thresholds employed. Alternate term is indefinite, or no opinion.
