I would say that is what makes its TOTALLY unjustifiable.
I am not so sure about that.
I think there are some cases where the evidence is so overwhelming it is absolutely crystal clear that a person is a killer. It is not so in George's case and in my opinion he should not have been convicted in the first place.
In Huntley's case the police showed that one of the girls had been bleeding in his bathroom. Where the area that the girls bodys were dumped he knew very well, also that one of the girls phones was switched off for the last time right outside Huntley's house. Huntley killed those girls 100%.
There are others as well that absolutely catergorically murdered and in some cases mass murdered.
Dennis Neilsen killed 10+ men in his house, he eventually got caught because their remains were blocking the shared drains of the very building he lived in.
There is no reason why either should not be executed. The same with Peter Sutcliffe.