The title question says it all, here's some background as to why I am asking: I just thought about something and wanted to check with the experts at Mi Yodeya who have learned Makkot or the relevant halachot.
In general, the conditions required to convict in a murder case are so steep that it would take a particularly "murderous court" to achieve a successful conviction even twice in 70 years (Makkot 1:10).
What happens to people who murdered someone with witnesses, but something like the witnesses failing to warn him occurs (not sure if that applies to murder cases?), so he isn't put to death? Is there any other form of penalty, such as exile*?
If not, if the murderer is just released back into the public, this is a bit difficult, because doesn't Sefer HaChinuch mitzvah 410 state that one of the reasons the manslaughterer is made to go into exile is in order to give the family of the victim peace, as they do not have to look upon their relative's killer day in day out. The Torah seeks to create a pleasant atmosphere (not to mention a safe one, without known murders running around!)
What of cases of actual murder? Everyone knows he did it, he's been spared on a technicality and released, and he did it on purpose so it's a much worse situation.
So, what exactly happens to people who murdered but were not convicted on a technicality?
* Even that would require some sort of explanation as much of the laws of exile to cities of refuge is based around the fact that the person simply made a grave mistake and isn't a murderous person.