According to research from the University of Sydney and...

According to research from the University of Sydney and Macquarie University, there has been a reduction of firearm related homicides since the Howard gun laws were introduced. There has also been a reduction in firearm suicides too. Source: https://www.theguardian.com/world/2...s-shootings-and-reduced-homicides-study-finds

Although, I am unsure if there has been an over drop in overall homicides, is per your original point.