Criminal Justice

Is the Death Penalty a Deterrent?


From the AP via the Cincy Enquirer comes a story about whether executing criminals is a deterrent to future homicides:

…a series of academic studies over the last half-dozen years that claim to settle a once hotly debated argument—whether the death penalty acts as a deterrent to murder. The analyses say yes. They count between three and 18 lives that would be saved by the execution of each convicted killer….

"Science does really draw a conclusion. It did. There is no question about it," said Naci Mocan, an economics professor at the University of Colorado at Denver. "The conclusion is there is a deterrent effect."

A 2003 study he co-authored, and a 2006 study that re-examined the data, found that each execution results in five fewer homicides, and commuting a death sentence means five more homicides. "The results are robust, they don't really go away," he said. "I oppose the death penalty. But my results show that the death penalty (deters)—what am I going to do, hide them?"

Statistical studies like his are among a dozen papers since 2001 that capital punishment has deterrent effects. They all explore the same basic theory—if the cost of something (be it the purchase of an apple or the act of killing someone) becomes too high, people will change their behavior (forego apples or shy from murder).

In 2005, there were 16,692 cases of murder and nonnegligent manslaughter nationally. There were 60 executions….

More here, including rebuttals and rebukes from critics, an overview of past controversies, etc.

I am against the death penalty because I think the state should use the least amount of violence to protect people from criminals. That said, I think it's always worth knowing the actual effects of policy (or at least debating them). I've got no idea if the new research is better than older research that led to different conclusions. But it's certainly worth talking about (and in as broad a context as possible, one that factors in social factors that range beyond immediate effects on crime rates).

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  1. I realize you wrote this really, really early in the morning, but I don’t think you meant to say “I don’t think the state should use the least amount of violence . . . ” It would make more sense without the “don’t.”

  2. Does this demonstrate that it is a deterrent?

    I mean, I am not quite sure how it would deter crimes of passion (a spouse killing another spouse in an unplanned fit of passion) or crimes of compulsion (serial killers).

  3. Because as a person contemplates committing a murder, he thinks to himself, “Gee, I’m willing to spend the rest of my life in prison over this, but am I willing to be executed for it 20 years from now?”

    I can see that these economists have spent a lot of time with criminals.

  4. I am against the death penalty because I don’t think the state should use the least amount of violence to protect people from criminals.

    Nick, if this study is correct, you have answered yourself. The appropriate amount of violence is to use the death penalty in cases of homicides.

    I have opposed the death penalty because of the possibility of mistakes and because I have doubts about a deterrent effect. If there is a significant effect, then it is time to re-evaluate. DNA evidence is also making verdicts more accurate.

  5. A 2003 study he co-authored, and a 2006 study that re-examined the data, found that each execution results in five fewer homicides, and commuting a death sentence means five more homicides.

    How on earth do they get this kind of precision? Do they ask the five extra killers, or what?

    I can see how the cost argument works, but it seems to me that the way the death penalty is executed (no bad pun intended) in this country dilutes the cost argument too much for it to have an effect. Then again, there’s always the psychological effect of having a death penalty in place.

    Either way, there are things we can do to reduce crime which have far clearer effects than the death penalty–reduce gun control laws (makes the de facto death penalty far more immediate), reduce welfare (which facilitates the breakup of family units, leading to more crime), lowering taxes/tariffs/economic controls in general so people have more opportuniy, and make the justice system focus more on restitution to victims so that society will have greater respect for property rights.

  6. I could care less if the death penalty deters murders, which apparently it does. If someone purposefully takes the life of another, they must pay with their own life. It is the only equitable way to deal with it.

  7. Maybe the deterent effect would be greater if ti didn’t tkae 20 years and if it wasn’t “easier time” to be on death row than general population.

    Let’s take a vote!

    Reuters reported:

    Conducted for the Death Penalty Information Center, a group that opposes capital punishment, the poll showed 62 percent of those surveyed support executing convicted murderers.

  8. I’m constantly amazed that people distrust the government in regard to money, taxes, the environment, national security, religion, abortion, morality, education, roadbuilding policy, mining inspections, catching dogs, drunk driving BAC levels, redlight cameras, parking tickets, drug policy, illegal drug policy, medical coverage, the national debt, state contract review and allocation, public library policies, and a whole host of other things, but many of these same people trust the government with our lives.

    I’m against the death penalty because government can fuck things up. And placing responsibility in the hands of a jury doesn’t make that any less true. I work in a prison and see many people who probably deserve to be killed, but I also see evidence of the grossest prosecutorial misconduct imaginable. (Note: don’t talk to your lawyer using the Maricopa County Jail phone system unless you want the prosecutors to have access to your privileged conversations, too.)

    As to the statistics, I think the number of murders and homicides versus the number of executions makes almost any analysis of human behavior idiotic. Maybe a future study can prove that winning the lottery is a deterrent to buying lottery tickets.

  9. Maybe a future study can prove that winning the lottery is a deterrent to buying lottery tickets.

    FWIW, after my stepdad matched 3 numbers and won $500 he started buying twice as many tickets.

  10. the amount of time and effort required to execute a person (from time of arrest to time of execution) makes it so almost completely pointless to even bother with. Aren’t there fates worse than death that we can have active immediately, like being locked in a cell where you are constantly bombarded with e-harmony commercials? While the damage is irreversible, at least you can compensate wrongfully accused people with money. You can’t do that for a dead person.

  11. The death penalty will deter the murderer from murdering again.

    All snarkiness aside, I used to be 100% in favor of the death penalty until the debacle that is the death penalty process in Illinois. I believe 6 out of 13 inmates on death row were later found to be innocent.

    I also used to be in favor of a speedier appeals process. Fortunately for those 6, they had enough time for someone to prove their innocence.

    Maybe other states have their act together. If so, I am still in favor of the death penalty in those states, just not in Illinois.

  12. Corrected mistake pointed out by Karen. Thanks.

  13. KenK,

    How is death row “easier time”? I think most on death row would gladly join the general population for the outside air, exercise, inmate jobs, programs, ability to talk to people casually, see their family in person, and all the rest. Isolation may sound like a spa vacation for some, but it tends to make inmates insane.

  14. It’s always nice when the evidence confirms the theory, but I don’t think there was ever any serious doubt that the death penalty served to some extent as a deterrent. Raise the cost of something (like crime) and people will consume less of it.

    The question remains whether the death penalty deters crime sufficiently to warrant its use. No, it probably doesn’t affect some crime of passion homicides at all (blind rage is blind rage, but not all rage is blind) or homicides where the perceived rewards outweigh the risk of capture, conviction and execution.

    Between these extremes, the question is whether it is worth the lives of, let’s acknowledge the findings, from 3 to 18 persons to give the state the power to kill its own citizens. Reasonable people will disagree, but I don’t think it is and think the better question is not how many lives are saved per execution but how much the average risk of being the victim of a homicide increases.

  15. Aren’t SWAT teams are making such cumbersome statutes obsolete? Where y’all been?

  16. D.A.R.,

    Well, one would also have to weigh it against the average number of innocent people executed every year.

  17. “I could care less if the death penalty deters murders, which apparently it does. If someone purposefully takes the life of another, they must pay with their own life. It is the only equitable way to deal with it.”


    It makes no difference whether it deters somebody else or not. The murderer took a life and therefore must forfeit his (or her) own. That is justice pure and simple.

  18. Grotius, I agree that’s a factor as well.

    I have no problem per se with the “that’s justice” argument. For all I care, serial killers could be executed, resuscitated and executed again however many times they took other people’s lives. That still doesn’t make it a good idea to give the state that power.

  19. “Is the Death Penalty a Deterrent?”


  20. Foxnews was rolling in this story like a dog in urine, which made me instantly suspicious of it…

  21. I believe there is another study which instead of using criminals executed as a variable, uses the introduction of death penalty laws. The idea being, when the penalty was introduced did it have a detering effect? The conclusion was no it didn’t, but I don’t know the validity of the study or who did it, when they did it, where they did it, etc. I just read about it in the Armchair Economist.

  22. It makes no difference whether it deters somebody else or not. The murderer took a life and therefore must forfeit his (or her) own. That is justice pure and simple.

    Pure and simplistic, perhaps. Even if we all agreed that a murderer deserves to die, that doesn’t answer the question of who the murderers are. Our policy concerning what to do with murderers must take into account the fact that we often make mistakes about who the murderers are. Our policy should contain room to make amends should a mistake be made. Capital punishment allows for no such remedy.

    That, and the race issue.

  23. We need a death penalty simply because no executed criminal ever committed another murder.

    But because any system would be fallible, I would let old age pull the switch.

  24. Do we really need the death penalty? My requirements for addressing “really bad crimes” are

    (1) Deter the population from committing the crime by creating a culture where we understand that certain crimes aren’t tolerated (2) Prevent the perpetrator from committing the crime again (3) Restore to the victim as much as possible.

    The death penalty seems to accomplish 1 and 2, but there are less severe/problematic ways to accomplish them.

  25. The cum hoc ergo propter hoc logical fallacy can be expressed as follows:

    * A occurs in correlation with B.
    * Therefore, A causes B.

    In this type of logical fallacy, one makes a premature conclusion about causality after observing only a correlation between two or more factors. Generally, if one factor (A) is observed to only be correlated with another factor (B), it is sometimes taken for granted that A is causing B even when no evidence supports this. This is a logical fallacy because there are at least four other possibilities:

    1. B may be the cause of A, or
    2. some unknown third factor is actually the cause of the relationship between A and B, or
    3. the “relationship” is so complex it can be labelled coincidental (i.e., two events occurring at the same time that have no simple relationship to each other besides the fact that they are occurring at the same time).
    4. B may be the cause of A at the same time as A is the cause of B (contradicting that the only relationship between A and B is that A causes B). This describes a self-reinforcing system.

    In other words, there can be no conclusion made regarding the existence or the direction of a cause and effect relationship only from the fact that A is correlated with B. Determining whether there is an actual cause and effect relationship requires further investigation, even when the relationship between A and B is statistically significant, a large effect size is observed, or a large part of the variance is explained.

    I will go with point number 3 on this issue.

  26. This article is failing to see an even bigger picture.

    When you have the option of execution as part of your criminal justice system, you send a very simple mesage to the general population, namely that it is OK to take another person’s life.

    Fact is it is never right to take another person’s life. None of us has that right to do this, not you, not me, and definitely not the government on behalf of you and me.

    Murder is wrong, period.

    Is it any wonder there are so many murders. We live in a society where the government itself says ‘it’s OK to kill’ and that sets the tone for the rest of us.

    We need to send a message especially to young people growing up in this society that murder is so wrong that not even the government can do it.

    Until we do that we will continue to have the appalling murder statistics that we have.

    Frankly you are only seeing a very small part of the picture when you claim the death penalty acts as a deterrent.


    1) You can push a button that will kill a murderer convicted on the basis of solid DNA evidence. You are certain based on statistical studies that by doing so, you will on average deter 5 future murders. Do you push the button?

    2) A runaway train is headed right for 5 people drinking beer and partying on what they think are out of service tracks. You have your hand on a lever that will divert the train to a different track, where one person is partying. If you don’t act, five people will die. If you do pull the lever, one person will die. Do you pull the lever?

    3) You are a doctor in a hospital. You have five patients who will die within the day if they don’t get organ transplants from different parts of the body. If they get the transplants they will live healthy normal lives. A healthy former patient walks in the hospital who, by an extraordinary coincidence, you remember is a match for all five patients. You can kill and dismember that person in a back room and no one will ever find out what happened. Do you kill the healthy patient to save the lives of the five other patients?

    4) If had differing answers to these three questions, killing one to save five in some instances and not others, why?

  28. (1) I don’t push the button, despite my being “certain” about the statistical realities (not that I could ever achieve such certainty). The “victims” are not real, in the sense that there will be no murders causally related to my particular failure to push this particular button.
    (2) I pull the lever. In this case, I have to directly kill somebody–that much is certain. So it is best to minimize the number of dead, all else being equal.
    (3) I do not kill the healthy patient. I would not want to get in the habit of killing people to help others unless the killing was forced, the numbers notwithstanding (the train-lever habit is one I would want to acquire, by contrast, although I would probably quit if that situation kept happening). After all, I might start killing people I dislike or don’t know to help my friends.

  29. In the Killing Quiz above, in all three cases the ethical thing to do is to kill one person to save five lives. What is important is the good of society, not the good of any given individual. And if the majority of voters agree with me, then you have consented to this due to your acceptance of the implied social contract, unless or until you leave the country.

  30. Is the Death Penalty a Deterrent?

    No. Neither is life in prison, in fact, neither is prison itself.

  31. Let’s accept that each execution prevents 5 murders. So the 60 executions in 2005 prevented 300 of 17000 murders, or lowered the murder rate by 2%. Is this worth the expensive machinery of running capital punishment? Could the same money have been used on better policing? Each execution costs on the order of several million dollars. That’s a lot of cops.

    Do I, personally, feel that this 2% decrease in my risk of being murdered overcomes my distaste at being part of a society with capital punishment? No, I don’t. Speaking for myself, I’ll accept the 2% greater chance of being murdered.

  32. Look,

    The Justice System works perfectly Fine…as long as u r not involved.

  33. Has anyone asked how an execution works to deter people? I suspect that the huge amount of publicity surrounding the execution has the effect. Maybe we should try an experiment and put petty criminals in stocks in public spaces and let children throw tomatoes at them. See if that convinces people not to park illegally.
    Seriously though, if you could figure out what part of the publicity convinced those few anguished people to not kill, you could maybe convince people not to murder without having to go through the execution.

  34. The cum hoc ergo propter hoc logical fallacy can be expressed …

    I think the preferred phrases is Post hoc ergo propter hoc so not to confuse it with Latin for “hard-core porno money shot.”

  35. I’m surprised to see no mention of celerity. Hasn’t it been known since Bentham’s day that celerity of punishment — and the high probability of same — and not severity, provides the most effective deterrent?

    When you see the umpteenth study of a severe punishment’s deterrent effect, I immediately suspect that the scientist or the funders are trying to avoid work on the real troubles with our criminal justice system: poor police work and long and expensive trial process.

    Further, I bet an armed citizenry (or a high percentage of citizens armed with private firepower, or even throwing knives) would deter many more crimes. That’s celerity; you don’t have to wait for days or weeks for retaliation, there’s an immediate defense possible in play during a crime.

    To argue that all killing is wrong, as one writer does, above, prevents private self-defense, too. Calling all killing “murder” is simply persuasive definition, and not very helpful. Murder is “wrongful killing”; saying it is wrong is a pleonasm, and not a very effective rhetorical pleonasm at that.

    To argue that killing a convicted murderer sends “a very simple message to the general population, namely that it is OK to take another person’s life,” begs the question: which is more important?

    * the idea that it is wrong to kill an innocent person, or

    * that even killing a person guilty of killing innocents is bad?

    Most people do not believe that killing a person in self-defense is as bad as killing an innocent to rob them. Most people don’t believe that a soldier killing an enemy during a war is as bad as killing one’s next-door neighbor. By making blanket condemnations of homicide, you actually run against the grain of a lot of ingrained morality, much of it common sense. You need a whole lot more argument than provided here.

    I have argued, in the past, that killing a murderer puts a sort of palpable balance to the moral community, asserting by the negative act the positive value of the innocent, thereby honoring the rights of the innocent. By not killing the murderer, one sleights the rights of the innocent dead.

    The only trouble with this view is the prevalence of error in the process, and the killing of further innocents, the innocents accused and found guilty (in error).

    To balance this problem, most reasonable people decide against allowing capital punishment until the justice system be fixed.

    Few argue more creatively. One could, for instance, make death penalty mandatory for police officers and prosecuting attorneys who illegally suppress evidence or fabricate false evidence in capital crime cases.

    But perhaps that’s too creative a solution.

  36. Though fairly conservative, I have always been against the death penalty. (voted that way against in the last election). However, I also said If they could show it was a deterent, I might change my mind. Maybe time to re-evaluate?

    As for mistakes, how about this? If the prosecutor wants the death penalty, the standard changes from “reasonable doubt” to guilty beyond any doubt.

  37. I tend to think the best deterrent to crime would be some certainty of getting caught.

    Changes need to be made.

    1. Repeal victimless crime laws.
    2. Modify rulings that disallow evidence in technical violation.
    3. Make law agents accountable for their violations of rights.
    4. and so on

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