https://doi.org/10.1177/0093854818811379 CRIMINAL JUSTICE AND BEHAVIOR, 201X, Vol. XX, No. X, Month 2018, 1–25. DOI: 10.1177/0093854818811379 Article reuse guidelines: sagepub.com/journals-permissions © 2018 International Association for Correctional and Forensic Psychology 1 LAYERS OF BIAS A Unified Approach for Understanding Problems With Risk Assessment LAUREL ECKHOUSE University of Denver KRISTIAN LUM Human Rights Data Analysis Group CYNTHIA CONTI-COOK JULIE CICCOLINI The Legal Aid Society (New York) Scholars in several fields, including quantitative methodologists, legal scholars, and theoretically oriented criminologists, have launched robust debates about the fairness of quantitative risk assessment. As the Supreme Court considers addressing constitutional questions on the issue, we propose a framework for understanding the relationships among these debates: lay- ers of bias. In the top layer, we identify challenges to fairness within the risk-assessment models themselves. We explain types of statistical fairness and the tradeoffs between them. The second layer covers biases embedded in data. Using data from a racially biased criminal justice system can lead to unmeasurable biases in both risk scores and outcome measures. The final layer engages conceptual problems with risk models: Is it fair to make criminal justice decisions about individuals based on groups? We show that each layer depends on the layers below it: Without assurances about the foundational layers, the fair- ness of the top layers is irrelevant. Keywords: risk assessment; race; algorithms; sentencing; crime prevention; decision-making; prediction; violence risk assessment W hen someone is accused of a crime, should they be held in jail or released to await trial? Once someone has been convicted, should they be sentenced to imprisonment, or released on parole or probation? In most states, judges make these decisions based on presentations by counsel for the prosecution and defense, either in writing or orally (or AUTHORS’ NOTE: The authors thank the Human Rights Data Analysis Group, the National Science Foundation Graduate Research Fellowship Program, the Horowitz Foundation for Social Policy, and the Travers Department of Political Science at UC Berkeley for support for this research. We also thank Patrick Ball, Josh Norkin, William Isaac, and Christopher Shea for valuable feedback. We also thank Emily Salisbury, Jody Sundt, and Breanna Boppre, as well as two anonymous reviewers. Correspondence concern- ing this article should be addressed to Laurel Eckhouse, Department of Political Science, University of Denver, 2199 S. University Blvd., Denver, CO 80208; e-mail: laurel.eckhouse@du.edu. 811379CJB XX X 10.1177/0093854818811379Criminal Justice and BehaviorEckhouse et al. research-article 2018