Two days ago, we asked whether lawyers (or anyone else) can recognize reasonable doubt (or its absence) when they see it. Yesterday we stepped back to ask the question: What is the right standard for “reasonable doubt”? Should you convict when the probability of guilt is 70%? 80%? 90%? Of course the answer might vary with the crime and the prospective punishment. To keep this discussion concrete, I’ll focus on capital punishment for murder, and to keep it simple, I’ll pretend that no other punishment is available (so that the only choices are “acquit” and “execute”).
Today I want to take yet another step back and ask: What is the right standard for deciding the right standard? Here are two possible meta-standards:
1. Minimize the suffering of innocents.
2. Minimize suffering.
The difference is in whether we choose to care about the suffering of murderers.
Let’s be clear about what it means to apply the first of these meta-standards:
Lowering the reasonable doubt standard from, say, 95% to 90% means that more innocents will suffer from false convictions while fewer innocents will suffer from being murdered (either by killers freed to kill again or through the weakening of deterrence). To assess the trade-off, suppose for illustration that in a land of 300 million people, there are 300 cases a year where the defendant just clears that 90% hurdle. Of these, 30 (that is, 10 percent) will be innocent. Any given citizen has a 30/300,000,00 = .0000001 chance of being among these innocents. (That’s six zeroes.) On the other hand, freeing all 300 of these defendants means there will be (say) 3 additional murders. Any given citizen has a 3/300,000,000 = .00000001 chance of being among those victims. (That’s seven zeroes.) If you’re out to minimize the suffering of innocents, then the question is: Which do the innocents prefer — a tiny chance of being murdered, or a ten-times-greater chance of being falsely convicted? If people generally prefer the first, we should lower the reasonable doubt standard to 90% (or possibly lower). If people generally prefer the second, we should maintain a higher cutoff.
To turn this into a concrete answer, you’d of course want to use more realistic numbers, which would include a realistic estimate of the deterrent effect, and a realistic estimate of which risk is preferable.
The second meta-standard is similar, but it also accounts for the fact that murderers, like the rest of us, prefer not to be convicted of murder. And, of course, any one of us might turn out to be a murderer someday (or at least might have been born into circumstances that would have led us to become murderers). So the tradeoff becomes: A 300/3,000,000 = .00001 chance of a murder conviction (possibly deserved, possibly undeserved), versus a .0000001 chance of being murdered. (That’s seven zeroes versus five zeros.) Would you prefer a tiny chance of being murdered or a hundred-times-greater chance of being convicted, possibly falsely, possibly not? Based on this calculation, you’d be a lot less likely to lower the reasonable doubt cutoff.
Which is the right meta-standard? Blackstone said it was better for ten guilty men to go free than for one innocent to suffer, suggesting that there’s something special about the suffering of innocents. (And also, though it’s not relevant here, apparently forgetting that the entire tradeoff he was addressing is between the suffering of innocents on the one hand, and the suffering of other innocents on the other hand.) But it’s not completely obvious how you’d justify this distinction. Our personalities and our life circumstances are assigned to us randomly. If John happens to be born with a more murderous personality than Jane, it does not clearly follow, as a matter of public policy, that we should put less weight on his interests.
No matter which meta-standard you adopt, you’ll probably also want to adjust it for the fact that when the reasonable-doubt threshhold is set too low, it invites abuse by manipulative prosecutors. It’s easier to fake evidence that someone is 70%-likely to be a murderer than to fake evidence that someone is 90%-likely.
Which meta-standard seems right to you? Or do you have a better one?