Given the consistency of the current findings with the general offender rehabilitation literature, we believe that the RNR principles should be a major consideration in the design and implementation of treatment programs for sexual offenders. [...] The Maryland scale assumes that the reviewers are interested in the conclusions of the different studies rather than aggregating the data through secondary analysis. [...] The CODC Guidelines express the consensus opinion of experts concerning the features that increase or decrease the confidence that the results are an unbiased estimate of treatment effectiveness. [...] However, evidence of meaningful and predictable variations in the findings based on the quality of the interventions would support the position that the results of the available studies are determined by more than design artefacts. [...] The items concern the extent to which the study’s features introduce bias in the estimation of the treatment effect, or influence the confidence that can be placed in the study’s findings.