title: The MATS-1 Risk Assessment Scale: Summary of Methodological Concerns and an Empirical Validation.
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.
authors.affiliation: Forensic Assessment Group, Ottawa, ON, Canada lesliehelmus@yahoo.ca.
authors.forename: Leslie
authors.initials: L
authors.lastname: Helmus
authors.affiliation: Sand Ridge Secure Treatment Centre, Mauston, WI, USA.
authors.forename: David
authors.initials: D
authors.lastname: Thornton
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D057237:Criminals; D006801:Humans; D008875:Middle Aged; D012008:Recurrence; D018570:Risk Assessment; D055502:Secondary Prevention; D012742:Sex Offenses / Q000517:prevention & control*; D011795:Surveys and Questionnaires
keywords: MATS-1; Static-99; prediction; risk assessment; sex offenders