Journal of the American Academy of Psychiatry the Law

Michael S. Purcell, JDJennifer A. Chandler, LLB, LLM and J. Paul Fedoroff, MD


The use of phallometric evidence by Canadian criminal courts has steadily increased since the early 1980s. Phallometry was initially considered by courts to be a potentially useful tool in the determination of accused persons’ culpability; however, its contemporary use is limited to the postconviction contexts of sentencing and dangerous and long-term offender applications, as one of several means of diagnosing offenders, determining recidivism risk, and assessing treatment prospects. We provide an overview and assessment of the use of phallometric evidence by Canadian criminal courts and conclude that its contemporary application appears to be consistent with the expert psychiatric consensus on its proper role and function in the forensic context. We further identify potential difficulties associated with the adequacy of offenders’ consent and the occasional divergence of expert opinion about the reliability and validity of phallometry for diagnosis and risk assessment.

Phallometry (also known as penile plethysmography) is a technique used in the assessment and treatment of paraphilias in men. In essence, it detects an increase in penile circumference in response to specific visual or auditory stimuli and, on this basis, suggests the nature of the subject’s sexual interests. Analogous techniques have been developed to assess women. We note also the recent exploration of functional magnetic resonance imaging to assess sexual interests. Phallometric evidence has been accepted by courts in the United States as a condition of parole, probation, and supervised release; however, there has been much greater resistance to admitting it at trial.

Although phallometry has now attracted a significant level of acceptance for its utility in the treatment of paraphilias and to some extent in making prospective risk assessments, a much more controversial use has been the reliance on phallometry to draw retrospective conclusions about whether an accused person is guilty of an offense. The Supreme Court of Canada rejected the use of phallometry for this purpose in 2000 in the case of R. v. J.-L.J.

The use of phallometric evidence first appeared in Canadian criminal cases in the 1980s, and references to it have increased substantially, up to a current frequency of 25 to 30 new case references per year. (The frequency of case references is presented graphically in Figure 1.) It is most frequently used by Canadian courts in sentencing convicted offenders, where information about diagnosis, risk of recidivism, and prospects for successful treatment are being considered.

The purpose of this article is to provide an overview of the contexts in which Canadian criminal law is currently using phallometric evidence, as well as to offer a discussion of some potential difficulties in that use. In particular, we comment on whether an offender can be said to consent freely to phallometric testing in the forensic context. Second, we note that the literature suggests some divergence between experts on the reliability and validity of phallometry for diagnosis and risk assessment, and this debate sometimes surfaces in the contending expert opinions in court. Given the particular strengths and limitations of phallometry as a forensic tool, it is important that expert testimony clearly explain areas of disagreement among experts and the precise limits on what phallometry is capable of telling a court about diagnosis, prospects for treatment, and risk of recidivism.

Read the full Paper at: Journal of the American Academy of Psychiatry the Law

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