The implications of these decisions for policy and practice are unclear. This article predicts the effect of various pretrial preventive detention policies on the amount of time defendants would be required to spend in jail and the amount of crime that would be prevented due to their detention. Eighteen potential pretrial preventive detention policies are examined in 7 jurisdictions. The findings call attention to the increases in jail use and small reductions in pretrial crime that would be associated with each policy. (Publisher abstract).