Assume a simple civil case in which there are two essential elements in the plaintiff's cause of action, A and B, and no complicating affirmative defenses or counterclaims. The proper mathematical interpretation of the preponderance of the evidence standard in civil cases, we are
told, is that the probability of the event to be proved must be greater than .5. Therefore, a mathematical interpretation of the plaintiff's burden is that the plaintiff should win if, and only if, the probability that both A and B are true is greater than .5. That is to say, if Pr is the probability function, which is taken to satisfy the mathematical calculus of chances:
P wins if and only if Pr(A and B) is greater than .5.
However, we are told that this is not equivalent to the established legal standard. Rather, we are told, the legal standard is that the plaintiff wins if and only if each element is severally proved by a preponderance of the evidence. Accepting the mathematical interpretation of the preponderance of the evidence standard, this would have to mean: P wins if and only if Pr(A) is greater than .5 and Pr(B) is greater than .5.
A typical, though obviously unrealistic, example of the difference between the two standards is to assume A and B are probabilistically independent and that Pr(A) = .6 and Pr(B) = .6. Then, under the multiplicative rule of mathematical probabilities, Pr(A and B) = Pr(A) x Pr(B) .36, so that the plaintiff loses.
I think that people on a jury have the ability to take into account the full action and make this point mute. Meaning they see the full case and then decide the elements. Even if they were to give some probabilistic number to each element it is merely made up. They then are really just deciding based on feeling if the person is guilty or not. If so, who cares how we divide up the elements.
I can totally be wrong, but I think that folks applying a preponderance standard mostly look at the whole story (all the essential elements) and ask: do i believe this story more than I dont believe this story? and that sort of avoids this issue because it looks at the total probability.
@Sirius, do you think that concept applies to decisions in general, or primarily in examples like OP's? Since we are fundamentally deciding probability by feeling alone without a universal probabilistic metric just in general.
When deciding element by element, I don't think juries consider the elements like "gates" where, once a gate is passed (i.e. an element has 51% probability) the jurors stop considering that case and treat the element as though it is 100% proved
We can't always attribute numbers to actions and evidence. If to me, D committed the tort more likely than not after I consider all the elements, I'm siding with P. The question is: When is enough enough?
Yes @Bodrog, but that is what jury is. It is the people deciding. You will not achieve universal outcomes, but that is fine. The court should present what it wants and then the jury of the people should decide.
I think it's ridiculous that we don't take into account the conjunction of the elements of a crime. In a civil case maybe we're less worried, but consider a criminal case. If there are 5 elements to a crime, and we are 95% certain a defendant satisfies each individually, there is in reality only a 77% chance that he is guilty (.95^5). Don't we think that's way too low for beyond a reasonable doubt?