Does field reliability for Static-99 scores decrease as scores increase?

Area of Science:

• Forensic Psychology
• Criminology
• Psychometrics

Background:

• The Static-99 is a widely used actuarial tool for assessing sex offender recidivism risk.
• Accurate risk assessment is crucial for informing supervision, treatment, and legal decisions regarding sex offenders.

Purpose of the Study:

• To evaluate the field reliability of Static-99 scores across a large sample of sex offenders.
• To determine if rater agreement on Static-99 scores diminishes as the assigned risk score increases.

Main Methods:

• Analysis of Static-99 scores from 21,983 sex offenders.
• Comparison of initial and most recent Static-99 scores to assess rater consistency.
• Examination of score differences in relation to assigned risk levels.

Main Results:

• Rater agreement was lowest for high-scoring offenders.
• Static-99 scores were identical between initial and recent evaluations for only 40% of offenders initially scoring 6, versus over 60% for those scoring 2 or lower.
• Score discrepancies of 2 or more points occurred in approximately 30% of high-risk cases.

Conclusions:

• Measurement error in Static-99 scores may be greater for high-risk offenders.
• Findings highlight the need for procedures to minimize or account for measurement error in high-score evaluations.
• Implications for intensive supervision and civil commitment decisions based on high Static-99 scores warrant careful consideration.