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Sexual Predator Evaluations and Phrenology:

Considering Issues of Evidentiary Reliability

Terence W. Campbell, Ph.D. [*]

Behavioral Sciences and the Law, 18: 111-130 (2000)



Standards of evidentiary reliability 

Ethical Obligations and standards of practice 
Ethical Standard 2.02(a) 
Testing Standard 1.1 
Testing Standard 2.8 
Testing Standard  5.1 
Ethical Standard 2.04(a) and Testing Standard 6.1 

Generally used methods for risk assessment 
Unaided Clinical Judgment (UCJ)  
Continued Reliance on UCJ in Clinical Practice 
Guided Clinical Risk Assessments (GCRAs)  
Sexual Violence Risk-20 (SVR-20)   
Overview of GCRA

Actuarial procedures 
Rapid Risk Assessment for Sexual Offender Recidivism (RRASOR)   
Minnesota Sex Offender Screening Tool (MnSOST)  
Sexual Offender Risk Appraisal Guide (SORAG) 

Overview of available assessment instruments 




This article reviews six assessment procedures used for assessing the recidivism risk of previously convicted sexual offenders. The review of these procedures examines whether they comply with generally accepted ethical and practice standards. With few exceptions, most risk assessment instruments fail to comply with these standards. Currently used instruments for risk assessment continue to rely excessively on clinical judgment; and, as a result, they remain at a preliminary stage of development. Consequently, these instruments amount to experimental procedures; and, therefore, they cannot support expert testimony in a legal proceeding.


In response to public outrage provoked by highly publicized sexual assaults, various states have enacted sexual predator legislation (including but not limited to Arizona, California, Florida, Illinois, Kansas, Minnesota, North Dakota, Ohio, Washington, and Wisconsin). These laws call for a civil hearing to determine whether a previously convicted sexual offender should be indefinitely committed for treatment. If committed for treatment as a sexual predator, the individual remains confined until another hearing finds that his response to treatment warrants release. Sexual predator laws also typically require that two or more psychologists or psychiatrists evaluate the previously convicted offender .

Sexual predator evaluations typically proceed in a step-wise manner to address three questions:

(i) Has the offender been convicted of sexually violent predatory offenses against two or more victims?

(ii) Does the offender have a diagnosed mental disorder that predisposes the person to the commission of criminal sexual acts?

(iii) Is the offender likely to engage in sexually violent criminal behavior as a result of his diagnosed mental disorder?


Sexual predator evaluations therefore raise questions regarding the evidentiary reliability of the assessment methods used to evaluate previously convicted offenders. In other words, do these assessment procedures possess sufficient evidentiary reliability to support expert testimony in a legal proceeding?

Assume, for example, that a psychologist testifying in a sexual predator hearing premises his or her opinion on a phrenological assessment of a previously convicted offender

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(phrenology, of course, is an entirely discredited method of personality assessment involving measurements of the shape and curvature of the head). Relying on phrenology, the psychologist concludes that the previously convicted offender does -- or does not -- qualify for civil commitment as a sexual predator.

Quite obviously, any court would disallow the testimony of a psychologist using phrenology in the manner described above. Phrenology is neither generally recognized, nor generally accepted, for psychological or psychiatric assessment. Instruments generally used for risk assessment are obviously more reliable than phrenology. The question remains, however, whether those instruments are sufficiently more reliable than phrenology to allow them into evidence in asexual predator hearing.

[*] Correspondence to: Terence W. Campbell, Ph.D., 4105 Metro Parkway, Ste 103, Sterling Heights, Ml 48310, USA; e-mail address: terence.campbeI13@gte.net