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. 
In June 2017, researchers unveiled a new version of the PPG test that utilizes virtual reality.  Subjects must wear 3D glasses while they watch extremely lifelike animated pornography. Billed as a “polygraph for pedophiles,” the new technique allows investigators to present a range of pornographic scenes in order to detect any inappropriate sexual interests. 
Proponents of the new technique say that it avoids the ethical concerns raised by critics of PPG testing in the past.  No longer must the government obtain or create its own pornography using actual human actors (a difficult task in the case of child pornography, which is illegal for anyone to possess).  According to the developers of the new technology, the immersive experience of virtual reality indulges the darkest fantasies of offenders and prevents the release of recidivists back into society.
In fact, however, PPG testing remains as unreliable and abusive as ever. Notwithstanding the recent technological advances, PPG testing has no value in estimating the risk of future sex crimes, and it subjects offenders to an Orwellian nightmare that our Constitution -- and basic human decency -- cannot abide. 
One of the most fundamental problems with PPG testing is its inaccuracy. An offender’s excitement or inhibition when viewing pornography in front of government officials does not necessarily reflect that offender’s true proclivities. Even if the PPG shows that certain images cause arousal, there is a dubious link between this arousal and future lawbreaking.  Numerous studies have exposed the unreliability of PPG in predicting recidivism. 
No less an authority than Guido Calebresi, the former dean of Yale Law School, who is currently a judge on the Second Circuit Court of Appeals and opined that PPG testing lacks “any value as correctional treatment.” According to Judge Calebresi, there is scant evidence indicating that PPG monitoring is “reliable or therapeutically beneficial.” 
Ironically, PPG testing may exacerbate the problem of sexual abuse. The images shown to convicted sex offenders could actually fuel their prurient interest.  Some offenders may be able to “beat the test” by focusing on thoughts that dampen their arousal while they view images that would normally be exciting. Studies indicate that as many as 80% of subjects can cheat the PPG test in this matter.  Officials who place undue faith in PPGs might release offenders prone to committing further sexual assaults. 
Leaving aside questions of its effectiveness, PPG testing is objectionable because it is highly invasive. It punishes “thought crime.” As the Supreme Court famously observed a half- century ago, “[o]ur whole constitutional heritage rebels at the thought of giving government the power to control men’s minds.”  The U.S. has never imposed criminal penalties on defendants who simply ponder impermissible subjects. Such punishment would violate the First Amendment, which protects freedom of thought as well as freedom of speech.  Even in Roman times, the judiciary observed the maxim cogitationis poenam nemo patitur (no one is punishable solely for his thoughts).
PPG testing entangles the government in the enterprise of producing and showing pornography. The replacement of human actors with highly lifelike 3D animation may address one harm of pornography -- the exploitation of performers -- but it does not sidestep the basic moral problem of PPG testing: this procedure purposefully evokes instincts that the government deems immoral.  Treating a pedophile by showing him high-tech child porn is akin to treating a meth addict by giving him highly potent meth.
The danger posed by PPG testing calls out for nationwide regulation. Historically the Supreme Court has set vague parameters for the treatment of sentenced offenders, and has let local jurisdictions determine what punishment and rehabilitation are appropriate.  This approach has led to inconsistent rules for the use of PPGs. The time has come for a comprehensive audit of the entire process for punishing and rehabilitating sex offenders. To combat pedophilia and other sexual abuse, we need closer scrutiny of the overall penal response -- not just the penile response of individual offenders.
 United States v. McLaurin, 731 F.3d 258, 260 (2d Cir. 2013). Accessed June 29, 2017.
 Donna J. Drucker, “The Penile Strain Gauge and Aversion Therapy: Measure and Fixing the Sexual Body,” in The Machines of Sex Research: Technology and the Politics of Identity, 1945-1985, 25-28 (2014). Accessed June 29, 2017. http://www.springer.com/cda/content/document/cda_downloaddocument/9789400770638-c2.pdf?SGWID=0-0-45-1404814-p175267160 4 Tom Waidzunas, et al, “‘For Men, Arousal Is Orientation’: Bodily Truthing, Techmosexual Scripts, and the Materialization of Sexualities Through the Phallometric Test,” Social Studies of Science, Jan. 8, 2015, at 189. Accessed June 29, 2015. http://journals.sagepub.com/doi/pdf/10.1177/0306312714562103
 Max B. Bernstein, “Supervised Release, Sex-Offender Treatment Programs, and Substantive Due Process,” 85 Fordham L. Rev. 261, 261 (2016). Accessed June 29, 2017. http://ir.lawnet.fordham.edu/cgi/viewcontent.cgi?article=5231&context=flr
 Petition for Writ of Certiorari, Williams v. United States, filed with U.S. Supreme Court on June 24, 2015, at 15. Accessed June 29, 2017. www.scotusblog.com/wp-content/uploads/2015/10/Cert- Petition.pdf
 Waidzunas, supra n. 4, at 189.
 “Utah Prison Tackling Problems with Sex Offender Treatment,” U.S. News & World Report, May 22, 2017. Accessed June 29, 2017. https://www.usnews.com/news/best-states/utah/articles/2017-05-22/utah-prison-tackling-problems-with-sex-offender-treatment
 Oregon Revised Statutes 144.270(4)(b). Accessed June 29, 2017. www.oregonlaws.org/ors/144.27
 E.g., United States v. Cheever, slip op., 15-CR-00031-JLK, at 16 (D. Colo. July 28, 2017). Accessed June 29, 2017. https://casetext.com/case/united-states-v-cheever
 Stacy Liberatore, “The Virtual Reality ‘Polygraph for Pedophies’ Being Used to Assess Sex Offenders,” U.K. Daily Mail, June 8, 2017. Accessed June 29, 2017. www.dailymail.co.uk/sciencetech/article- 4586580/Virtual-reality-used-assess-sex-offenders.html
 Olivia Solon, “Polygraph for Pedophiles: How Virtual Reality Is Used to Assess Sex Offenders,” The Guardian, June 7, 2017. Accessed June 29, 2017. https://www.theguardian.com/technology/2017/jun/07/virtual-reality-child-sexual-abuse-pedophile-canada-research
 Patrice Renaud, et al., “Using Immersive Virtual Reality and Anatomically Correct Computer- Generated Characters in the Forensic Assessment of Deviant Sexual Preferences,” Virtual Reality, March 2014, 37-47. Accessed June 29, 2017. http://link.springer.com/article/10.1007/s10055-013-0235-8
 Cheever, supra n. 10, at 15.
 United States v. Weber, 451 F.3d 552, 570-71 (9th Cir. 2006) (Noonan, J., concurring). Accessed June 29, 2017. http://caselaw.findlaw.com/us-9th-circuit/1420924.html
 Bernstein, supra n. 5, at 272-78.
 Allegra M. McLeod, “Regulating Sexual Harm: Strangers, Intimates, and Social Institutional Reform,” 102 Cal. L. Rev. 1553, 1593-94 (Dec. 2014). Accessed June 29, 2017. www.californialawreview.org/wp- content/uploads/2014/12/06-McLeod.pdf
 McLaurin, supra n. 2, at 263.
 Jason R;. Odeshoo, Of Penology and Perversity: The Use of Penile Plethysmography on Convicted Child Sex Offenders, 14 Temp. Pol & Civ. Rts. L. Rev. 1, 43 (2004). Accessed June 30, 2017. http://heinonline.org/HOL/Page?handle=hein.journals/tempcr14&div=3&g_sent=1&collection=journals
 Roy O’Shaughnessy, “Phallometry in Court -- Problems Outweigh Benefits, 43 J. Am. Acad. Psych. & L. 154, 157 (2015). Accessed June 30, 2017. http://jaapl.org/43/2/154
 Science Daily, “Sexual Treatment Programs in Prisons, Hospitals Are Ineffective,” Jan. 25, 2015. Accessed June 30, 2017. https://www.sciencedaily.com/releases/2015/01/150127212341.htm
 Stanley v. Georgia, 394 U.S. 557, 565 (1969). Accessed June 29, 2017. http://supreme.justia.com/cases/federal/us/394/557/case.html
 Cheever, supra n. 10, at 15.
 Odeshoo supra n. 19, at 34.
 Bernstein, supra n. 5, at 283-87.
The opinions and views expressed through this publication are the opinions of the designated authors and do not reflect the opinions or views of the Penn Undergraduate Law Journal, our staff, or our clients.
A Note from the Author:
This article is based on research for an affirmative case in policy debate. I am grateful for guidance I received from Alexander Erwig, a student at Harvard Law School, who was my debate coach and instructor in debate classes at the University of Oregon until June 2017. Thanks also to my father Tom Lininger, a law professor at the University of Oregon, who helped with editing this article.