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.