Osler's Razor

One of the important debates in my field is about deterrence: specifically, the question of "does a long prison sentence (or a death sentence) given to one person deter others from committing a crime?

Sadly, the debate is mostly between people who know what they are talking about (on one side) and people who have no data, just "how they feel." The former think that deterrence is insignificant based on data or experience, while the latter believe deterrence happens and is very important because that is how they feel it should work.

Take a look at this report from the National Institute of Justice, a branch of the US Department of Justice. There isn't much bias here-- one would expect, after all, for the DOJ to support the idea that its actions deter crime and thus are worthwhile.

Instead, here are the five key (and interrelated) data points the report sets out:

1) The certainty of being caught is more important in deterring crime than long sentences.
2) Sending someone to prison is not a very effective way to deter crime.
3) Police can actually reduce crime by increasing the perception that people will be caught and punished.
4) Increasing the severity of crime does little to deter crime.
5) There is no proof that the death penalty deters crime.

In terms of what we do on the ground, it is the first point that is most important (and if we pay attention to it, the others will follow). Quite simply, solving more crimes is more important than punishing crimes harshly if the goal is (as it should be) to reduce crime.