Thursday, July 13, 2017

Preponderance of evidence

I do formal epistemology, but I am no legal scholar, so this could be a complete misunderstanding. It is my understanding that in civil cases a preponderance of evidence standard is used on which the evidence needs to support the conclusion with a probability merely greater than 1/2. This seems ridiculous in cases where one is seeking compensation for damages that may or may not have occurred.

Suppose I run a business, and I treat my staff somewhat shabbily but not actionably. One day, hundreds of dollars worth of damage occurs in the server room. Review of blurry security camera footage, building security logs and other data proves beyond reasonable doubt the following facts:

  • A thin stocking was put over the camera, hence the blur.

  • There were five employees in the offices at the time, all of whom had a similar build and appearance: Alfred, Bill, Carl, David and Edgar.

  • Three of the employees went to the bathroom and returned with buckets full of water which they poured over the servers.

  • The other two employees did their best to stop the three, including calling 911 and heroically trying to block the door to the server room. As a result of the scuffle, everybody’s fingerprints are on the buckets and everybody is wet.

  • Each employee claims with equal credibility that he was one of the two trying to stop the attack. Moreover, everybody claims to be unable to identify who the “other” employee trying to stop the attack is. The video footage shows a scene of such confusion that this inability to identify is unsurprising.

So, I fire all five employees and then sue each of the five individually for damages. I argue in the case of each employee that the evidence clearly yields a 3/5 probability that he was responsible for damage, and remind the court that 3/5 > 1/2.

But surely it would be a serious miscarriage of justice for all five to be held liable for damages that two of the five sought to prevent.

I wonder if cases like this get their force solely from the fact that the probabilities involved—namely, 3/5—are low, or if there is something else going on. Suppose I had a thousand employees, and 999 were damaging company property while one was trying to stop it. Should I be able to sue all 1000, correctly claiming a probability of 999/1000 of responsibility in each case, while knowing for sure that a judgment in my favor in all 1000 cases will place a severe financial burden on exactly one innocent person?

That is an uncomfortable conclusion, but perhaps we should bite the bullet and say that this is no different from a court knowing that over the run of many cases, there will be a small minority where innocents are burdened with grave burdens—and the risk of suffering such burdens is just part of the cost of membership in the society, much as being subject to the draft is.

But it seems much more uncomfortable to say something like this in the 3/5 case—or a 51/100 case—than in a 999/1000 case.

Naive intuition: The evidence needed should scale with the burden to the defendant in the case of a finding against them. Maybe the evidence requirements do thus scale in practice. Like I said, I am no legal scholar.


Kolten Ellis said...

I believe that juries must be instructed to convict only if the evidence shows "beyond a reasonable doubt" that the defendant is guilty, which is to say that any doubts remaining in the case would not affect whether a reasonable person would still find the defendant guilty.

According to the Cornell law school site, preponderance of evidence is used as the standard in civil court, but not criminal court. Presumably the lower stakes for penalty and absence of pending criminal censure are supposed to justify a lower standard by way of saving resources, expediting the process, etc.

Kolten Ellis said...

In this case then, there is a reasonable doubt about each particular person's havig commited the crime, thus leaving no particular employee in serious danger of being imprisoned. The ambiguity in the term 'reasonable doubt' may well also fit your idea of scaling the level of stringency needed for a declaration of guilt - the more outlandish the crime, or more serious the crime relative to average crimes, the less likely a priori someone is to commit such a crime. In such cases, the same lines of evidence constituting doubt would have a larger impact on the probability calculus than for a crime which has a higher base probability of being committed.

Alexander R Pruss said...

The case I was describing is specifically a civil case: the employer is suing the employees for damages.

SMatthewStolte said...

I am not a legal scholar either, but I have a rough picture that I use to think about this issue. (No doubt, it is mistaken in some ways.)

I've always thought of the difference between civil and criminal cases to be the difference between reparation and retribution. I know there are some problems with thinking of the difference this way, but it helps explain the reason for different standards of evidence. If I am accused of a crime, and the point of the punishment is retribution, then the court is really only deciding whether and how I am to be harmed. We say that it is better to presume that I am innocent, because we think it is better to refrain from harming a guilty person than to punish an innocent person. But if I am simply involved in a civil case, the question does not just concern me; it also concerns the party who brought the case. Suppose a case where you sue me and the question is: Who should pay for damaged equipment? Should I pay for it or should you pay for it? I have been refusing to pay for it, so you brought the case to court. If the court wrongly rules in my favor, then you will be wrongly harmed; if the court wrongly rules in your favor, then I will be wrongly harmed. This parity is going to be maintained whether repairing the equipment costs $100 or $1000. We say the standard of evidence required should be just slightly over 50% in order to reflect this parity. But of course when we are talking about money, there are other options: the court could rule that I should pay for half the cost of the repairs or a third or a quarter. Will they sometimes take options like these on the grounds of uncertainty about which party is in the right?

Alexander R Pruss said...

That's promising. Maybe in my case the problem isn't just about probabilities but about the fact that (most likely) being in debt for their portion to the employer (which from the numbers I gave is going to be at least $40,000) is one that, while not a punishment, is a "punishing burden", one that may well cripple the employee for years. And we generally sympathize more with the little guy.

Let's see if I can re-tell the story without the big-guy vs. little-guy kind of distraction. Sally is poor and lives in a trailer park, and she borrowed $20,000 to buy a trailer. At night, three of her five equally poor neighbors burned down her trailer, and there is no evidence as to which three of the five it is. She is now in debt $20,000. She sues each of the *five* for $4,000 each, and let's suppose that she wins. It's tough luck on the two innocent neighbors, but one could look at it this way: *somebody* innocent was going to be out a lot of money, and it was either going to be Sally or one of her neighbors, and at least the innocent neighbors are only out $4,000 each, rather than Sally being out $20,000.

It's an unjust *outcome*, but the injustice isn't the fault of the legal system, which has tried to clean up after a bad situation, but of the three people who burned down her trailer. The legal system in this case redistributed the burden more evenly. (And I know that some legal scholars do think in redistribution terms.)

And the above setup actually fits with your suggestion that the court should scale the damages based on probabilities, even though I never mentioned such scaling. Each of the three guilty neighbors owes Sally $20,000/3 (keeping to just the financial damages for simplicity). Each of her *five* neighbors has a 3/5 probability of being of the three guilty ones. So, it's plausible to think that each should be made to pay (3/5)($20,000/3)=$4,000.

Still, even on the redistribution of burden story, there is a question of why the end result should have Sally bearing none of the burden. The starting situation was: Sally is burdened. The end result is that three guilty neighbors are burdened (good!) and two innocent neighbors are burdened, but Sally has no burden at all (we assume). It seems a little unfair that Sally's two innocent neighbors bear a burden but Sally does not. But I'm not sure, I could go both ways.

Anyway, so it's not glaringly unfair if all the six parties in the story are more or less on par financially, or when the five suspected of the crime are much richer than the victim. That's interesting.

But in cases where they're not, application of the more-likely-than-not standard can result in a worse distribution of burdens than before. Suppose that the company is wholly owned by an employer who is filthy rich and can absorb the cost of server room repairs simply by selling one of her many luxury cars. But now the moderate burden on the employer is shifted to a crippling $40,000 debt held by each of two unjustly fired employees (who have no recourse about their firing, because more likely than not, the court will say, they were worthoy of firing), plus perfectly fair $40,000 debts held by each of three guilty employees.

Alexander R Pruss said...

An actual legal scholar wrote to me and told me of Cohen's Paradox of the Gatecrashers. You've got 1000 people at an event, and you know that only 499 bought tickets. Presumably, there are no receipts or anything like that (shoddy record keeping). So can the organizers sue all 1000 people for crashing the gate?

So, unsurprisingly, this is ground that has been well gone over by legal scholars.

I am still a bit intrigued by the twist in my original case provided by the fact that two of the five employees deserve a *reward* for trying to stop the other three. Of course, the legal system doesn't hand out rewards, but it seems wrong to knowingly impose harsh treatment on two people who deserve to be rewarded for how they acted in that very situation.