Individuals accused of sex crimes may have incentive to mis-report sexual preferences. As such, there have been attempts to develop more objective, physiological measures of preferences.
Penile Plethysmography
Clinical assessment for paraphilias in the Czech Republic often involves penile plethysmography. This entails the offender placing a “strain gauge” over his penis and watching a series of pornographic slides. The types of pornography depicted often include heterosexual sex, homosexual sex, group sex, bestiality, rape scenes, and child pornography. The theory is that sexual orientation (such as toward children) can be assessed via the patterns of penile engorgement in response to the categories of slides.
Visual Reaction Time
The Abel Assessment for Sexual Interest (AASI) entails the offender watching a series of 160 slides (in 22 categories) of clothed individuals who range in age from pre-schoolers to adults. Measures include, for each photo, length of viewing time and self-report of arousal/disgust. Though the AASI is non-invasive, questions have been raised about its reliability and validity.
Polygraphy
Though polygraphy can be an effective means of obtaining a sexual offense history and increasing the number of disclosures made by the offender, its validity as a means of identifying the veracity of claims has been strongly questioned.