With the vast number of screening instruments presently being used to determine drug abuse and drug dependence in various populations, one would expect that sufficient instruments would be available for criminal justice clients. However, the most widely used instruments have not been sufficiently normed on this distinct client population (Swartz, 1998).
The most popular assessment instruments were designed for individuals seeking admission and treatment to a drug rehabilitation program. The primary goal of such assessment tools is to assess and classify addicted clients who are acknowledging that they have a substance abuse problem and who are seeking help for that problem based on their own motivations (Swartz, 1998).
One of the most commonly used substance abuse instruments is the Addiction Severity Index (ASI), a comprehensive instrument that examines the substance problem area, legal problems, and family/social problems (McLellan et al., 1992). Because of the instruments breadth it is popular in comparison to the assessment tools that only examine the frequency of substance abuse. The diverse areas allow for the assessments of functional impairment required for appropriate DSM-IV diagnosis and treatment considerations.
McLellan and colleagues (1992) showed the ASI to be a reliable and valid assessment inventory among substance abusers applying for treatment. Workers in related fields have used this information to support there usage of the ASI with other types of substance abusers. The ASI has been used for sentencing, correctional, and in parole or probation environments to evaluate substance abusers within the criminal population. The designers of the ASI state that while they did work with a number of researchers within these areas, there has not been any published studies determining the instruments reliability or validity within the populations (McLellan et al., 1992).
While the non correctional instruments provide a more in depth assessment of functioning, it is difficult to use these instruments validly because the base rates of the normative sample are not formulated on a correctional population. The base rate is a statistical measure of the prevalence of an assessed behavior over a set period of time and in a specific population. Base rates are the fundamental statistic in psychometric evaluation and is seen as the most important type of information in assessments (Webster, Harris, Rice, Cormier, & Quinsey, 1994). If a clinician undertaking an assessment uses an instrument validated on a population unique from the normative sample and does not modify the estimates for the unique context of prediction significant errors could result (Monahan, 1981; Shah, 1978).
