Well, we can do tests for psychopathic traits, and other things. My point basically revolves around that ability to rehabilitate someone, which is something we can actually quantify to a good degree.
I thought we were assuming that the people in question both intentionally, knowingly killed a person. We're past manslaughter or cases of plain mental deficiency. We say "well the wife's crime is a little more excusable because we know her husband was doing something bad," but that's the same as saying "this lady's husband deserved to die more than the person randomly chosen by this psychopath." Shaky ground to be making judgments on, IMO.
As to the first sentence, good point. However, I don't see how it's all like comparing the two people murdered. In fact, it's not even considering the people murdered at all, but rather the intent, motive and identity of the person killing. Justice is towards that individual, so justice should be dependent upon that individual. You
do agree intent matters, at least presence of, so I don't think it's really all that unreasonable to think that the intent of a love-torn / abused woman is different than the intent of a psychopathic killer.
Say the woman is being abused - her intent than is to escape abuse. A criminals is to have basic subsistence. Neither of these compare to a serial killers joyful intent.
And I agree, but so many cases don't neatly fit the paradigm like these examples.
I think that's why they're exceptions to the rule. I think it would be wrong for us to say that we can
never execute someone, ever, no matter the circumstance. It's a blurry issue, but I'm all for having actual execution being extremely rare, to avoid the controversial middle, and pick an area where it's still rather easy to tell what's going on.