Methods for estimating the crime commission rates of criminal offenders are discussed in the context of a potential selective incapacitation strategy that would assign different sentence lengths according to whether the estimated crime rate is above or below a specified threshold. Any such strategy is subject to error because the true crime rate of an offender may differ from his estimated crime rate. For two strategies having the same cost, one of them is favored over the other if it has a higher expected number of crimes averted or if it has a lower probability of assigning long sentences to offenders with low crime rates. Both of these criteria are met by using a Bayes estimate of the crime rate rather than a maximum likelihood estimate. This is demonstrated by calculating the distribution of true crime rates for offenders whose estimates are above a threshold.