While I don't necessary approve of the conclusion, there are many important points that people seem to underestimate. (Briefly, before discussing them, I suspect that what currently makes death penalty so expensive is all the legal processes around it, so if we replaced all death penalty with life sentence in prison, we would spend more money on the prisoners, but less money on the lawyers, potentially saving money on the net.)

The key part is: While the truly horrible people are few, they cause vastly disproportional damage, plus all kinds of secondary damage (the population living in fear, not trusting each other, spending more money on security, or just not trying many projects because of the perceived risk). Eliminating these people from the streets might change the situation dramatically, possibly in ways that many of us can't even imagine. It could change a low-trust society into a high-trust society, with various positive impacts on mental health and economy.

I have also seen similar dynamics in other situations. For example, in school, there is often one child in a classroom that constantly keeps disrupting lessons, frustrating the teachers and reducing the learning opportunities for all their classmates. Removing that one child can dramatically change the entire experience for everyone involved. I have seen incredible changes during a week or two when the disruptive child got sick; but after their return the situation reverted to the usual.

There is a related problem, that crime is often difficult to prove (beyond the shadow of doubt, without doing something illegal yourself, etc.). For example, rape is often only witnessed by the two people involved; we get a "he said, she said" situation. Another example, in Slovakia the law about illegal drugs was changed so that it is no longer illegal to have the amount of drugs you need for your own consumption; only selling drugs is illegal. Sounds reasonable at first sight (catching the dealers is strategically more important than catching the users)... until you realize that in practice, selling is almost impossible to prove. Because you would have to be there, at the exact moment. A police arriving five minutes later (which is already a super optimistic scenario) can't prove anything: all people involved will claim that no exchange happened, that everyone who has drugs on them has already arrived with them, that it is all for their personal consumption, and that all they wanted was to talk. So I have literally the situation that people are selling drugs on my street, they are not even trying hard to hide (other than making sure that no one is closer than 10 meters to them at the moment the money changes hands), and they do it with complete impunity. So again, we have a situation where worrying about being needlessly harsh to the users made the crime itself... not literally legal, but not punished in practice either.

Which suggest a need of another "tough on crime" approach, like: if X is a crime you want to prevent, but it is extremely easy to pretend that X is Y, and there is no good reason why Y should be legal... then maybe you should also make Y illegal, just to make sure that the people doing X actually get punished. Basically, when making laws about Y, don't think about Y in isolation, but also about all things that can be plausibly made into Y. Even if the punishment for Y is smaller than the punishment for X, it should definitely be nonzero, and if it happens repeatedly, it is very likely X in disguise, so the punishments for repeated Y should be comparable to X.

My paraphrase of Gandalf: "Many that die deserve life. Can you give it to them? Then do the next best thing, and deal out death in judgement to the many that live who deserve it." 

I'm a bit conflicted on the subject of death penalty. I do agree with the view some solution is needed for incorrigible cases where you just don't want that person out in general society. But I honestly don't know if killing them versus imprisoning them for life is more or less humane. In terms of steelmanning the case I think one might explore this avenue. Which is the cruelest punishment?

But I would also say one needs to consider alternatives to either prison or death. Historically it was not unheard of to exile criminals to near impossible to escape locations -- Australia possibly being a best example. 

> Imprisoning someone for one year in the USA costs in the order of 100,000 dollars

There surely must be some way to decrease that by *at least* a factor of 4 or so, possibly by an order of magnitude, if we wanted to?  (The poverty line for a 8-person household in the contiguous US in 2025 is $54,150.)  Surely that might involve treating prisoners in rather questionable ways, but still way less questionable than f---ing killing them, IMO.

Another objection I have is that [waaay too many things are considered crimes that shouldn't be](https://archive.org/details/threefeloniesday0000silv) -- what fraction of people in prison are there for reasons comparable to any of your examples?

"0.12% of the population (the most persistent offenders) accounted for 20% of violent crime convictions" https://inquisitivebird.xyz/p/when-few-do-great-harm

Have we considered cryopreservation as an alternative solution? It could protect society from dangerous offenders without resorting to irreversible execution, while potentially costing less than long-term incarceration. If medical and rehabilitative technologies advance, this would also preserve the possibility of future reform. Worth exploring as a middle ground that addresses both societal safety and moral concerns.

In a sufficiently wealthy society we would never kill anyone for their crimes.

In a sufficiently wealthy society, there're far fewer forgivable/tolerable crimes.  I'm opposed to the death penalty in current US situation, mostly for knowledge and incentive reasons (too easy to abuse, too hard to be sure).  All of the arguments shift in weight by a lot if the situation changes.  If the equilibrium shifts significantly so that there are fewer economic reasons for crimes, and fewer economic reasons not to investigate very deeply, and fewer economic reasons not to have good advice and oversight, there may well be a place for it.

We accept that innocent people die due to our actions all the time, and making a special exception here is an isolated demand for rigour.

This is also true for life imprisonment, actually. We'll be sentencing some innocent people to life imprisonment. And although perhaps some of them will be exonerated, it's a statistical certainty that not all of them will be, and a statistical certainty that therefore we will destroy some innocent people's lives piecemeal. But we're okay with that, or at least it doesn't get the ire that the death penalty does.

In fact, this is a general problem with all public policies. Anything you do that affects a large number of people is going to statistically kill a number of innocents, unless it's the absolute optimal policy. You can't avoid killing innocents whether you have executions or not.

I think the US has too much punishment as it is, with very high incarceration rate and prison conditions sometimes approaching torture (prison rape, supermax isolation).

I'd rather give serial criminals some kind of surveillance collars that would detect reoffending and notify the police. I think a lot of such people can be "cured" by high certainty of being caught, not by severity of punishment. There'd need to be laws to prevent discrimination against people with collars, though.

What do you think about exiling them to a zone where extreme criminals have to fend for themselves such as they did with Australia?

We would obviously have to significantly streamline the process, such that people are executed within 6 months of being caught or so.

This is one of the biggest hurdles, IMO. How do you significantly streamline the process without destroying due process? In the US, this would require a complete overhaul of the criminal justice system to be feasible.

Similar disclaimer: don't assume these are my opinions. I'm merely advocating for a devil.

If we're going for efficiency, I feel like we can get most of the safety gains with tamer measures. For example, you could cut off a petty thief's hand, or castrate a rapist. The actual procedure would be about as expensive as execution, but if a mistake was made there is still a living person to pay reparations to. I think you could also make the argument that this is less cruel than imprisoning someone for years—after all, people have a "right to life, liberty, and the pursuit of happiness", not a right to all their limbs and genitals.

Another thing we can do is punish not only the criminal, but their friends and family too. We can model people as having the policy to take certain actions in a given environment. The ultimate goal of the justice system is to decrease the weight of certain defective policies in the general populace, either through threat, force, or elimination. When we get good enough mindreaders, we can just directly compare each person's policy to the defective ones, and change the environment to mitigate defection. Until then, we have to make do with approximations, and one's culture, especially the shared culture among friends and family, is a very good measure for how similar two people's policies will be. So, if we find someone defecting, it makes sense to punish not only them, but their friends and family for a couple generations too.