Criminality isn't absolute, it requires the context of what those in charge decided shouldn't be done.
Innocent under whose eyes ? one man’s revolutionary is another man’s terrorist. what morality and code stands the test of time ?
actions which was legal and moral say 200 years ago would be illegal and amoral now , who is to say how 200 years in future would see our framework for ethics from now ?
Taking any sentient life is a crime against nature and humanity.
Societies supporting death penalty are not civilized for the same reasons any cannibals are not.
Killing is killing, what difference does it make if you were hungry or felt scared or vengeance or merely sadistic to justify it .
The methods to establish innocence or exonerate[1] in legal systems objectively are extremely difficult or impossible. People will never be able to agree on who is innocent, no matter how obvious it looks to you or me.
DNA evidences have exonerated many in the recent years, many of the executed were mentally ill, a lot of the evidence is circumstantial and based on unreliable testimony which all too frequently is racially colored, there is no certainty they did the act they are accused of, let alone deserve to die for it.
The only meaningful consensus that can actually make a difference is that death penalty should be abolished.
It is barbaric and morally abhorrent,it is also not ineffective as a punishment, is not deterrent, and also extremely expensive.
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[1] Pardons is not one of them, pardons require admission of guilt
[2] Innocent Americans that is, we are quite fine with "collateral damage" of women and children without any due process in drone strikes or now in Gaza.
We still have different state governments in the US and different country governments around the globe. Are you more confident in those because its larger groups of people deciding, and enforcing, what is right and wrong?
1)Eliminate individuals targeting other individuals at a personal level on a routine basis.
2) An officially worded notice, as opposed to some thug threatening at you.
3) Some written text that has has a resembles of order call the 'law'. To give an analogy consider why religions texts appeal to people. People have a lot of reverence for the written word including areas where IMO it should not be relevant: example marriage.
To highlight my point, if a thug were to go around extorting people for money verbally on a periodic bases which are _less_ that the taxes currently paid and provided _more_ services than the government then the targeted individual of the extortion would more resentful than he/she would have been of the government.
Respect for institutions is really a sticking point for me though. For one thing, they need to earn and deserve our respect. For another, if respect for institution is the goal then those institutions shouldn't need the power to impose their will upon us.
I don't need someone to that I have respect for to force my hand, and if someone does force my hand I likely won't respect them.
(Unless you accept the self-reinforcing circular definitions of crime and state authority based on neighbors individually not having power over you but collectively having authority, and that somehow you consent to this by being born and not running away to another patch of dirt also under a similar tyranny of a different cloth.)