Objectives: Discussions of fairness in criminal justice risk assess-
ments typically lack conceptual precision. Rhetoric too often substi-
tutes for careful analysis. In this paper, we seek to clarify the tradeos
between dierent kinds of fairness and between fairness and accuracy.
Methods: We draw on the existing literatures in criminology, com-
puter science and statistics to provide an integrated examination of
fairness and accuracy in criminal justice risk assessments. We also
provide an empirical illustration using data from arraignments.
Results: We show that there are at least six kinds of fairness, some
of which are incompatible with one another and with accuracy.
Conclusions: Except in trivial cases, it is impossible to maximize
accuracy and fairness at the same time, and impossible simultaneously
to satisfy all kinds of fairness. In practice, a major complication is
dierent base rates across dierent legally protected groups. There is
a need to consider challenging tradeos.
