There are other effects of short prison terms to consider.
Now, don't misunderstand me and believe I'm painting Norway to be this fairy tale country where everyone is nice and good at heart. Scum can be found anywhere, also in Norway. But one thing that is very rare is murder to conceal other crimes, like killing witnesses, rape-victims, etc. The police have very good statistics on their website, so I can quote exactly how many if anyone is interested (
Can be found here, for those that understand Scandinavian languages.). The prison sentences for whatever crime they've committed are so short anyway, why risk prolonging it that much by also committing murder? Now, if they faced decades of prison for their crimes, it makes much more sense to go to extreme lengths to avoid getting caught, including murder.
This also includes murder. If you've murdered someone, and you know that if you get caught, you will spend the rest of your life in the hellhole of American prison justice, how desperate does that make you? Does this make you more dangerous until you're caught? Does the Norwegian system make it easier for murderers to give up without a fight, knowing how our system works?