I wish I can choose 'Appeal to Emotion.' That's what this is. No evidence brought. It's all subjective emotion.
Argument To Pity
This doesn't have any real substance to it at all. Nobody is saying that it's good in *all* cases, the point of the argument is that it's good in *some* cases. By bringing up these other cases, you're implying that they're *all* that way, without giving any real evidence except your emotions.
The only reason I can agree with this is because of the "some cases" part. If one could, for example, guarantee with 100% accuracy that someone murdered their parents in cold blood, this would be a fairly good candidate for the death penalty.
I'm not sure that I agree with your conclusion. The people who did so would be absolved of guilt because they did not make the decision; society at large would have condemned the person to death, not the executioner, who acts amorally, not immorally.
Only in the most extreme cases could it be considered. There needs to be absolute irrefutable evidence of guilt and no chance of personal reform of the guilty person. The execution of warcriminals after WW2 is an example of when it can be considered.
So death penalty should be applied more carefully, only if we are 100% sure that accused person really did it, for example if they were caught doing it or if court has very strong evidence (e.g. a video evidence). Any doubts should disallow death sentence from being executed.
Who or what decides whether or not a certain amount of doubt is acceptable to still apply? If a rule like that exists there have to be exceptions. If i kill 100 people, but there is considerable doubt over my methods or doing it would that be enough? or would it be down to a court to decide?