Acquitted but not necessarily innocent

We mentioned a while back that the way politicians’ reputations are besmirched by allegations of misconduct coudl be due to the mistaken recollections of their constituents. Of course, there are rational reasons to mistrust politicians who are investigated for misconduct too, as Stuart Armstrong points out:

more guilty people get tried and acquitted than the average of the population. So … the trial is evidence of guilt – noisy evidence, but evidence none the less.

So, barring a complete exoneration (rather than a mere acquittal) perhaps I am silly to have faith in people who’ve been tried for crimes or misconduct. Our justice system is designed to prevent the conviction of the innocent, rather than preventing the acquittal of the guilty. As such we should expect that far fewer people are wrongly convicted than are wrongly acquitted. Given that there are a reasonable number of convictions overturned in light of later evidence, it must be that plenty of those acquitted are guilty of what they are accused of. They can’ t be punished but that doesn’t make them innocent, and our beliefs should rationally reflect that.

5 replies
  1. Mike W
    Mike W says:


    Great to meet you last night. I had a good bit of time on the computer today. So I grabbed a look at your blog. You guys deserve a pat on the back for a good job. They’re great questions you’re asking. Keep it up!

    In regard to this question, have you thought that the utility function for defendants may not be symmetric? That is, there will be a lot more ‘disutility’ for an innocent defendant from a wrongful conviction than there will be utility for a guilty defendant from a wrongful acquittal.

    There have been countless episodes in the past of cases being wrongfully brought let alone cases with convictions that have turned out wrongful. Right now, even in little ol’ New Zealand, there are question marks over a good number of cases – the David Bain conviction overturned by the Privy Council, the unfinished Scott Watson case and, most recently, the arrest of prominent Maori activists in Police anti-terrorism raids.

    Imagine if you were an innocent defendant wrongly charged. Doesn’t it seem dangerous to do anything but follow the guilty until proven innocent approach of the courts as they take defendants to trial and appeal?

    Yeah, but good job asking questions like this! Spot you again somewhere around the traps, eh?


  2. Mike W
    Mike W says:

    Whoops! How’d that happen? In my fourth paragraph, of course I mean innocent until proven guilty not, as I have it, the other way around.


  3. rauparaha
    rauparaha says:

    Hey Mike, thanks for going to the effort of commenting. I absolutely agree with you: perhaps my post was badly phrased. I fully support the ‘innocent until proven guilty beyond reasonable doubt’ approach of our justice system. However, we should recognise that it is more likely to acquit the guilty than convict the innocent. Given that there are a number of cases where people are still wrongfully convicted, there must be many more where the guilty have been found not guilty by the courts. Thus, rational beliefs should increase the probability assigned to someone being a criminal when that person is charged with an offence.

    I am just pointing out that it is not irrational for suspicion to still hang over someone once they have been acquitted of a crime. It may not be fair to the vast majority of those acquitted who are indeed innocent but it is not irrational.

  4. Mike W
    Mike W says:

    Hey again James,

    Fair enough. I might have misunderstood your point in that regard.

    But there is still the problem that a defendant wrongly convicted feels so much worse than one wrongly acquitted.

    You may well be right that the law system is geared to making it more likely tha a guilty defendant is acquitted than an innocent one convicted. But, since the innocent one may already feel so much worse, how can you risk further hassling him when he may indeed be innocent?

    If everyone were to adopt your approach, innocent defendants may feel they can never shake the abatross from their neck. How can that be fair?


  5. rauparaha
    rauparaha says:

    Yes, you’re absolutely right. My aim here was to start from the observation that suspicion tends to linger over those who’ve been acquitted of crimes (eg. Clint Rickards) and try to explain why it might be the case. I certainly don’t condone the continued censure of those who have been acquitted. As you say, it’s very unfair to those who are truly innocent. However, it’s not inexplicable why this might be the case.

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