For Prosecutors, Can the Ends Ever Justify the Means?

I outline below a hypothetical that poses a moral dilemma for an imaginary public prosecutor.  This case vexes me, because I cannot seem to summon up a convincing argument that supports my intuitive reaction to it.  I would love to hear the perspectives of other philosophers.

Suppose you are a state’s attorney assigned to prosecute a heinous crime, say an especially horrible murder, with multiple aggravating circumstances. The defendant has been previously convicted of a number of violent felonies, so you have good cause to believe that if he is not executed or put away for life, public safely will be seriously jeopardized.

You have an overwhelming case against this defendant, sufficient to convince any neutral observer of the defendant’s guilt beyond all doubt. There is just one, potentially fatal, flaw. An absolutely key piece of evidence, without which you cannot proceed, was obtained in a manner that would, under prevailing judicial precedent, require that it be excluded at trial. There is nothing in these circumstances, however, that impugns its reliability as proof of the defendant’s guilt.

The “good news” is that you are the only one in the universe that knows the evidence is procedurally tainted. Perhaps the detective who secured the warrant leading to this evidence disclosed the infirmity to you, and has since died, and you are as sure as you can possibly be that this “technical” flaw will never come to light. The legal standards governing prosecutorial conduct are clear: you are required to disclose to the defense all exculpatory evidence, which will result in it being excluded, and the defendant walking free.[1] Should you comply?

I am troubled by the prospect of using the evidence, but am struggling to formulate a good argument to support my concerns. One obvious rubric for analyzing this dilemma is whether “the ends justify the means,” meaning whether a bad act is permissible in the service of a greater good. The obvious answer for a libertarian is “no,” because we are not permitted to treat persons solely as a means of achieving some supposedly greater good.

But this case seems different because we have by hypothesis a guilty person who deserves punishment, and who arguably has forfeited all procedural rights by his horrific crime. One plausible view is that these rules are in place to ensure that justice is done, i.e. to protect the innocent, and not to shield the guilty.

There is also the issue of whether agents are entitled to disregard at their discretion the cannons of legal ethics, when these rules that have a just purpose and are generally beneficial in application. There is something troubling about this violation, but I don’t see any obvious reason why rule worship is required in this case given the huge utilitarian cost. Why not ignore the rules when they would produce a terrible outcome?

So, I am left with the conclusion that the state’s attorney should violate his putative duties in these circumstances, but am very uneasy about this. There is probably a lot I have missed, and would appreciate your thoughts.


[1] See Lisa M. Kurcias, “Prosecutor’s Duty to Disclose Exculpatory Evidence,” 69 Fordham Law Review 1205 (2000),

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6 Responses to For Prosecutors, Can the Ends Ever Justify the Means?

  1. avraham says:

    Prichard I believe dealt with this. [That is from the school of the intuitionists]. But I do not recall off hand his approach. I think Dr Kelley Ross [of the Kant Fries school] must also have dealt with this somewhere but I forget where. I might try to look it up.

    • Mark Friedman says:

      Hi Avraham:
      I did a very cursory search, and didn’t see anything directly relevant in the literature. However, I am sure that others have considered this question, but I just didn’t have the time to run it down. I would appreciate it if you could bring these sources to my attention.

  2. Simon says:

    If the purpose of the rules is to protect the innocent and you “know” that the defendant is guilty, it seems there could be an argument that the rules should be circumvented. In your thought experiment, you do know that they’re guilty: in real life, will anyone be so sure?More worrisome, in my opinion, is that you, in effect, vouchsafe to uphold professional standards, but you would fail to do so if you transgress them. It seems to me that you therefore must not transgress them. It is a well known feature of due process that guilty people do go free. In many cases, there is a near certainty amongst the police and prosecutors that the defendant has committed a crime, but for all sorts of reasons the jury does not convict. This is the price that has to be paid to protect the innocent. I would be very reluctant to stray from this, even though I have a similar intuition to you about this case.

    • Mark Friedman says:

      Hi Simon,
      Both good points, but not decisive, I think. I did stack the deck with respect to “knowing,” but we often make critical decisions based on what we “know,” without requiring absolute certainty. For example, a decision to have a risky surgery performed. Or, when we legitimately kill someone in self-defense, even though there is a tiny chance that he really posed no threat (perhaps his gun was unloaded). So, I’m not sure the “let the guilty go free to protect the innocent” rationale works, when we have this level of confidence and releasing him will likely endanger the public.

      With respect to our prosecutor’s implicit promise to obey the rules, we often set this sort of obligation aside when the cost is too great. E.g., I promised to help you move, but then I suddenly needed to take my mother to the hospital. In any case, thanks for the comment.

  3. Simon says:

    Yes. We set aside promises when the obligation is too great. But promises can be a number of different things. At an informal level, they are an invitation to trust. At a legal level, they are a promise to deliver. In the latter case, there are not insignificant consequences – monetary compensation maybe, even imprisonment. In the former, the innocent party is, at least, deserved an explanation. Do you intend to provide an explanation to the professional standards body? If not, how do you justify the matter in terms of your own sense of integrity?

    • Mark Friedman says:

      I think you have correctly identified at least one of the things that make this case so hard. You are right that the prosecutor is “cheating” in some way and violating a duty. But the alternative as I have constructed it is that a murderer goes free, with a high probability that he will kill again. How do we balance the value of my integrity versus the practical danger posed by the latter? Would you feel comfortable holding a conversation with the mother of a future victim in which you disclose that the killer would have been imprisoned, but for your guilty conscience? There’s the rub.

      And, FWIW, I have a very similar gut reaction to yours.

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