Deterrence and Incapacitation: An Interrupted Time‐Series Analysis of California's Three‐Strikes Law¹

Abstract

Using uniform crime statistics, this research investigates the impact of California's three‐strikes law on instrumental, violent, minor, and drug‐related crimes over the first 5 years of the law's implementation. Autoregressive integrated moving average (ARIMA) models reveal little immediate impact of the law, but significant effects on instrumental crime over time, suggesting an incapacitation effect. After correcting for autocorrelation distortions, less restrictive multiple regression models that test simultaneously for immediate and gradual intervention effects disclose immediate (deterrent) effects on instrumental and minor crimes and arrests, and long‐term (incapacitation) effects on these and violent crimes as well. Drug‐related crimes appear impervious to the three‐strikes law under any analytic model, suggesting the unresponsiveness of such crimes to increasingly severe legal sanctions.