My Kepler Bb people are very anti-murder.
What I am proposing is that murderers get murdered but not with a typical murder weapon.
There are 3 types of murder that they are concerned with. Those are infanticide, homicide, and suicide.
Case 1: Infanticide
Infanticide is emotionally the worst murder of the 3 types. It is 1 thing if the baby dies of natural causes such as illness or starvation. It is a different story if the baby was killed by a criminal. Both lead to the mom crying a lot but infanticide also means that the mom and her surviving children go to jail because 1 or more babies were killed.
Whoever killed the baby/babies gets killed but not with your typical murder weapon. Burning would likely be a common way of killing a murderer.
Case 2: Homicide
Homicide, unlike infanticide, doesn't lead to anyone being in jail(Technically infanticide is a type of homicide but I consider it separate because of the results) but like infanticide, the murderer gets killed.
Case 3: Suicide
Of the three types of murder this is the best of them all. The reason is that this is self-murder. In other words the murderer is murdering itself instead of other people in this case. So the death penalty is already done and there is no reason to stop it if it is already done.
Philosophy behind it
Here is my philosophy behind this murder against murder.
If infanticide and Homicide are not actively stopped, more people will become murderers to defend themselves against other murderers. This can lead to death of the species, at least in a given area. Any death is sad but mass death due to defense is even worse than that. It will cause a lot of people to get angry which could in turn lead to more mass murder and it is just a vicious cycle that only police, lawyers, and the government can stop.
So, if a group of people deal with these infanticide and homicide cases by burning or asphyxiating the murderers, it will be so painful to the murderers that everybody else will not want to go through that same pain. So this discourages people from becoming murderers in the first place and thus the murder against murder works.
But would it really work and is it reasonable to not stop suicide because the murderer is murdering himself/herself?