> I would expect gangs to be more violent in the places where they are punished the same for nonviolent and violent crimes. If I'm in a gang and will go to jail for 40 years if I get caught distributing cocaine, I might as well murder if I think it will improve my position.

Conversely, how many police officers are killed in the US by criminals on the run? Exercise for the inclined reader: Compare with other western states.