Whenever some crime becomes prominent in the public eye, some politician inevitably promises to fix it by getting really tough on criminals. No more of this namby-pamby mollycoddling! This time, we’re going to make it so miserable to be a criminal that no one will dare .

It is a bipartisan habit; progressives may talk enthusiastically about ending mass incarceration, but switch the topic to male sex offenders (or, say, 2008 bankers) and what you’ll hear often sounds like a recap from some Republican law-and-order conference, circa 1984. The belief that crime is a soluble problem if we’re willing to be mean enough is apparently nestled deep in the human psyche.

Small wonder that President Trump, a firm believer in the healing power of meanness, thinks the solution to the opioid epidemic is to apply harsher measures. “We can be nice and we can be soft and weak, and you’re not going to have a country left,” he told a gathering in New Hampshire on Monday. “We have to strengthen up our laws . . . my Department of Justice will be seeking . . . much tougher penalties than we’ve ever had.”

“That penalty,” he said, “is going to be the death penalty.”

You can’t get much tougher than that. But however severe it sounds, however well it may poll, it remains a terrible idea that isn’t going to do much to fix the opioid epidemic.

At this point, some readers are probably sputtering. Harsher punishment for criminals doesn’t deter them, huh? What 1950 Intro to Sociology textbook did you get that out of?

Well, of course punishing criminals may help deter them. But believe it or not, the evidence that using the death penalty lowers crime is kind of . . . underwhelming. And no, you don’t have to be a squishy bleeding-heart to think so.

To understand why that might be, ask yourself why people turn to a life of crime. It isn’t just to make money, because the old saw is right: Crime really doesn’t pay, at least not well. It especially doesn’t when taking the risk of incarceration into account.

So why do we have so many criminals? As public policy researcher Mark Kleiman says, “Because they’re present-oriented and impulsive, with deficient capacities for shaping their current behavior in light of their future goals, and with poor judgment about their actual odds of getting caught.” If you severely underestimate your chances of getting caught, or if you live for the moment with little thought to the future, then increasing the severity of some far-off penalty won’t alter your decision-making much.

For that threat is pretty remote. Defendants enjoy a lot of procedural protections, and death penalty defendants get even more. That’s why death penalty cases cost the government a great deal more than noncapital cases.

And those are just the cases that go to trial, which most don’t. Prosecutors already rely on plea bargains in most cases. But how do you get someone to plea-bargain to the death penalty — promise them an extra-special final meal?

The answer is that you don’t. You use the death penalty as a threat to get them to plead to a lesser sentence. Which is one reason that in the entire country last year, just 23 people were executed.

Of course, a true draconian could just argue that we need to get rid of all those protections that make it hard to execute people. That notion would probably run into some problems with the Constitution. Even if that wasn’t the case, it would be apt to run into problems in the jury room. One of the problems with stiffer penalties is that the harsher the punishment, the more reluctant people are to impose it.

Insist on the death penalty, without “lesser included” offenses, and you are apt to see more hung juries or acquittals, at a higher cost. Include noncapital options, and the jury will often take them, leaving you at the old status quo, but again at higher expense.

So when it comes to the kind of people who become criminals — which is to say, people who are pretty bad at rationally weighing the future consequences of their actions — the death penalty is exactly the wrong deterrent. It makes punishment worse, but also, even less likely.

Not convinced? Remember that drug dealers are already living under the threat of the death penalty — from each other. With no legal recourse for contract enforcement, drug cartels often rely on violence to protect turf, punish people who cheat them, and occasionally, to open up a spot for personal advancement within their organization. If the threat of getting shot by a fellow street pharmacist doesn’t deter dealers, why would they be scared by an even more unlikely threat of getting caught, put on trial and eventually sentenced to lethal injection?

If we really want to deter them, we need to increase the odds of something bad happening to them right now . That means more law-enforcement officers on the streets; it also means more effective punishment models, such as the “swift, certain and fair” framework that has been advanced by Kleiman and others.

But it will also mean attacking the demand side with better treatment infrastructure. If there is one thing more than 40 years of the war on drugs has shown, it’s that taking out the supply chains simply doesn’t do much to reduce drug use. There are always new dealers willing to replace the old, and new distribution centers found when old ones are disrupted. If you really want to change anything, you have to reduce the demand those suppliers are chasing.

To be fair, the success rate of drug treatment is not all that high either, but at least it works sometimes — which is more than one can say for killing drug dealers. If that were an effective solution, dealer-on-dealer violence would have solved America’s drug problem decades ago.

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