Murder means the killing of the innocent.
Unlike war, death penalty, and killing as self-defense , to kill the innocent is immoral and unjust.
When your life, the society and/or the Country is in danger, killing as defense is objectively moral. Death penalty is done to those individuals who pose a great threat in society. War is objectively moral when is done as a defense from another Country. But, it’s objectively immoral/evil/wrong to kill the innocent. It is murder. It is always unjust to kill the innocent.