Advocates of the California version of the "Three Strikes and You're Out" law claim that it reduces violence and contributes to public safety by incarcerating violent offenders. However, there are no empirical estimates of the false positive rate (that is, the unnecessary incarceration of those who would commit exactly three and no additional "strikes") produced by the law. The authors estimate the false positive rate to be approximately 30 percent, causing a substantial human and financial cost with no advantage to public safety.