The Sentencing Project has a new report out that summarizes research on the effectiveness of criminal punishment as a deterrent.  It’s nothing pathbreaking, but it does offer a nice, succinct statement of the evidence against robust deterrence effects.  Here’s the conclusion:

Existing evidence does not support any significant public safety benefit of the practice of increasing the severity of sentences by imposing longer prison terms. In fact, research findings imply that increasingly lengthy prison terms are counterproductive. Overall, the evidence indicates that the deterrent effect of lengthy prison sentences would not be substantially diminished if punishments were reduced from their current levels. Thus, policies such as California’s Three Strikes law or mandatory minimums that increase imprisonment not only burden state budgets, but also fail to enhance public safety. As a result, such policies are not justifiable based on their ability to deter.

Based upon the existing evidence, both crime and imprisonment can be simultaneously reduced if policy-makers reconsider their overreliance on severity-based policies such as long prison sentences. Instead, an evidence-based approach would entail increasing the certainty of punishment by improving the likelihood that criminal behavior would be detected. Such an approach would also free up resources devoted to incarceration and allow for increased initiatives of prevention and treatment.

I’ll offer four reactions of my own.