I was speculating about how many people that murder (and don't get caught) go on to murder again. After consideration, I figured that the number would be relatively small - that is, that most folks probably aren't serial killers but are more likely to kill someone in an emotionally charged situation. Also, I figured that most people would be disturbed for the rest of their lives after performing such an act. Look how crazy OJ got. It destroyed him.
Ultimately, I think it would become common for most people to carry sidearms for purposes of self-defense. Anyone that was known to be a dangerous person would probably have a hard time in such a society. Once they became a known murderer, others would have an itchy trigger finger around them, and they would likely get killed if they continued being ornery.
I knew a fellow when I was living in Texas that pulled a gun on me one time. I told him to go ahead and shoot, but he didn't. He was known to be haphazard. Later, I told him that if he ever pulled a weapon on me again he better use it because I had already let him off the hook once. Then, here a couple of years ago, one of my old friends told me that he pulled a gun on a fellow at a bar, and the guy shot and killed him in self-defense.
Outlaws probably had a pretty short life expectancy in the early American West. Rugged folks don't put up with that nonsense.
I think most of the violence that occurs in the US today - besides domestic violence and that among friends - is associated with drug prohibition. I wonder how much violent crime would drop if all drugs were made legal? I know that there's some violence attributed with use, but I believe most of it is from the illegal trade and the environment it produces.
In a free society, if, for instance, a man murdered his wife, most people in the community would know or suspect him very strongly. They would be free to choose not to do business with him. He would likely lead a tormented life for the rest of his days.
After further consideration, I'm not sure that even a jury would be required as long as people communicated and were willing to defend themselves.
Nonetheless, I seriously doubt that the murder rate would exceed that of modern governments. Overall, there would very likely be much less people that were unnecessarily killed.