Gun control advocates believe that having more legally owned guns in a society makes that society more dangerous. It's an intuitive assumption, and an understandably compelling one, at least in theory. They also believe that handy guns lead to crime-of-passion murders, so they advocate for mandatory waits on gun sales and "safe storage" laws that mandate guns not be kept ready to fire.
In mid 2008, the Supreme Court struck down Washington DC's long-standing ban on civilian handgun posession, allowing District residents to legally buy and keep handguns in their homes. It also struck down DC's requirement that guns in the home be kept unloaded and locked up.
Gun control advocates predict carnage will follow, a perfectly reasonable prediction following their assumptions.
In the following year, DC sees its lowest murder rate since 1964.
Unlike many gun rights advocates, I _don't_ think this is definitely a causal relationship. The best statistical information we have suggests that easy civilian access to guns doesn't raise _or_ lower the violent crime or murder rates in any meaningful or consistent way. The culture and law enfocement sets your level of violent crime, criminals use whatever weapons are available, and in real life stabbing someone to death isn't actually much harder than shooting him to death. If adding guns in civilian hands really does deter crime or increase heat-of-the-moment murders, the two balance each other out.
So can we drop the "more guns more crime" myth already? It's sensible in theory, but like so many other sensible theories just doesn't bear out in practice.