The use of penile tumescence measures with incarcerated rapists: further validity issues.

The use of penile tumescence to categorize and assess the treatment of sex offenders has gained increasing popularity. Recent publications have expanded the use of tumescence measures for the classification of rapists. The majority of studies in the past using mainly subjects seeking treatment or admitting to difficulties in controlling rape urges have shown the technology to be a valuable asset in classification. The present investigation, however, points out the limitations of using this technology in certain populations. The responses of incarcerated rapists and incarcerated nonrape offenders were compared. Analysis of the data indicated that there were no significant differences between the responses of rapists and nonrapists and that the rape index proposed by Abel et al. (1978) did not reliably classify incarcerated rapists. This paper points out the limitations of penile tumescence assessment with certain populations and discusses possible reasons for the failure to discriminate in this investigation.