Why is it vengeance to want someone like Ian Huntley to be executed? he took 2 young girls lives, or Robert Black or Levi Bellfield?
There is no redemption, no forgiveness, they live out their lives very often taunting the families by refusing to say why or where they hide their victims or even if they killed them or not.
The DP certain isn't going to deter these people b i really don't see why they shouldn't also know the terror of knowing their life is about to end, it is no different than wanting them to be locked up for life.
If we re introduced the death penalty, it could be done where only the most heinous and clear cut of crimes would be punished by death.
Yes here is the argument about who does the execution and encouraging them but you could equally apply that to people who take delight in seeing someone locked up and join the prison service/police so they can inflict misery on prisoners.