depends on what you consider a modern(or more correctly developed, like you said in your first post) nation? Russia or even Brazil murder rates for example are FAR higher than ours. But if were comparing it mostly to the wealthy European nations then sure, but you cant even legally carry a knife in some of those countries. And in some of the asian countries(China, N Korea etc) the government is more likely to kill you before anyone else does because of the way their laws are setup. And i doubt well ever really know their true numbers anyway. And regardless, i rather live here where i can defend myself with my "god given" rights rather than live in tyranny.
And anyway, back on the main topic .... our prison system isn't fucked up because we put killers in jail, its fucked up because of retarded politicians who have flooded them with people who shouldn't be there. Someone selling dope definitely deserves to be locked up, but some doper who shoots heroin or smokes crack shouldn't be in jail for 25+ years just because he ran into bill clintons three strikes law. But yeah, our prison system is far from perfect.