In this hypothetical society, intentional Homicide (murder) is not a crime but society can develop normally and people carry out normal lives. I believe this could be possible because I read that apart from serial killers murder is rarely committed twice by the same person and nobody kills for fun or because they have a right to kill unless they have a mental illness.
Everybody has some moral and ethical quality (even the worst criminals) so I believe that even if we did not have any law saying that killing for whatever reason is illegal the average person would choose to not kill because most people have self-control and can manage their anger and impulses and most people naturally think it is unethical to kill without any penal code saying that murder is a crime and you could spend many years in a prison cell isolated from society if you did it. Even animals only kill for food or to protect their territory or to protect their offspring.
I wonder if homicide rates would be much higher than now or if life could be the same as today since there are many countries with high murder rates but they also have severe punishment and lifelong prison sentences for people who kill. The justice system would have fewer trials but the drawback is that if murder was legit people could think it is "normal" and " okay" to kill which could lead to future negative consequences.
Thousands of years ago before authorities created the first laws people used to murder each other since it always existed and murder still exists even with DNA recognition technology, cameras, life imprisonment and in more extreme cases death penalty. So I think murder is more about personal and emotional issues rather than the fear of the criminal system which might not appear to be a significant deterrent. But society worked before homicide became a legal crime.