This study uses California crime statistics for the years 1984-2004, to determine what effect, if any, the increased sentencing standards under the three-strikes legislation in California have had in deterring crime. This study follows a new approach in differentiating between the incapacitation effect and the deterrent effect of the law. Incapacitation is tested by tracking the change in prison population. Our results show that the three strikes legislation had a significant deterrent effect on total and property crime, but not so for violent crime. We find no support for incapacitation in the limited time period following the three-strikes legislation. (Contains 6 footnotes, 1 table, and 1 figure.)