For the prohibition, conservatively the homicide rate dropped 5-13%.
if about 15k people in the US are murdered every year. Ending drug prohibition would save lets say 10% of those murdered? or 1,500 people. thats about half the amount killed on 9/11. This isn't counting all the deaths south of the border or all of the violence.
https://mobile.nytimes.com/2011/10/02/opinion/sunday/the-not...