The Powers court noted the fact that it was unable to locate any decisions acknowledging the validity of penile plethysmography other than in the treatment and monitoring of sex offenders. Most, if not all, of the courts that have reached the issue of the admissibility of penile plethysmography tests have excluded evidence of the tests. Penile plethysmography cannot meet Daubert's validity or relevance tests because the test results are not generally accepted, are not sufficiently accurate, the test is subject to faking and voluntary control by test subjects, there is no standardized set of stimuli or scoring used by plethysmography experts and the results are not relevant to the question of whether the Defendant is a child molester. No test can determine whether a person will act on his feelings and desires. It would be like using a personality test to convict someone of burglary.
Plethysmographic data have no diagnostic value of any kind.
About one-third of offenders show no arousal in the lab. The proper stimuli to use are not pictures, but taped fantasies. Ideally taped fantasies spoken by the offender themselves, describing the offenders' own fantasies as well as contrived ones. The value in plethysmographic assessment is to aid the offender in learning how to control erection responses during deviant fantasy. That is it.