Citation

Helmus L, Thornton D. Sex. Abuse 2014; 28(3): 160-186.

Affiliation

Forensic Assessment Group, Ottawa, ON, Canada.

Copyright

(Copyright © 2014, SAGE Publishing)

DOI

10.1177/1079063214529801

PMID

24743657

Abstract

Recently, Wollert and colleagues proposed that sex offender recidivism estimates should be stratified by age and they developed an age-stratified scale called the MATS-1 (Multisample Age-Stratified Table of Sexual Recidivism). The purpose of this article is to highlight concerns with the development of the MATS-1 and to validate the scale using 3,510 sex offenders from 14 unique samples. Concerns with the scale's development fall into three categories: approximations leading to considerable loss of precision, absence of appropriate statistical tests, and the use of inappropriate statistical techniques. The predictive accuracy of the MATS-1 (Area Under the Curve [AUC] =.663) was significantly lower than Static-99R (AUC =.708). The MATS-1 also significantly underestimated recidivism for some offenders. Both the relative and absolute predictive properties of the MATS-1 were not stable across samples. We conclude that the MATS-1 is not appropriate to use for applied risk assessment. Proposals are made for alternate ways to develop risk scales using the age-stratification method.

Language: en