By Henry Lininger
Henry Lininger is a Wayne Morse Public Policy Scholar at the University of Oregon. His articles have appeared in publications affiliated with Cornell, Duke, and Yale.
Trigger warning: the content in this article may be offensive or obscene to some readers. Discretion is advised.
The U.S. justice system relies on an odd machine to assess deviant sexual arousal -- even though mounting evidence shows that this technique is inaccurate and abusive. Invented by a Czech scientist in the 1950s, the penile plethysmograph (or PPG) measures the engorgement of the male sexual organ.  It uses a cuff or other sensor to gauge blood flow.
Investigators employ PPGs to determine if certain categories of images cause arousal. The Czech government originally utilized PPGs as part of aversion therapy designed to “cure” homosexuals.  When social norms changed, this particular use of PPGs ended; however, PPGs remain in common use by corrections officials in the U.S.  District courts in virtually all federal circuits have included PPG testing as a condition for supervised release of sex offenders.  Nationwide, approximately 25% of sex offender programs utilize PPGs.