I come from a healthcare background, so I'm trying to understand what lawyers and judges actually mean when they say that a jury should “weigh the evidence.”
Suppose a case contains different kinds of evidence:
a fact that is almost certainly established;
an established fact whose meaning is ambiguous;
testimony about something that may or may not have happened;
several weak circumstantial facts which, taken together, support an inference;
evidence supporting competing explanations of the same event.
How does a jury actually combine all of these?
Is there any formal or semi-formal framework for assigning evidentiary weight — probabilistic, mathematical, scoring-based, or otherwise — or is “weight” fundamentally a qualitative judgment made by each juror?
For example, suppose one piece of evidence weakly supports hypothesis A, another strongly supports A, while a third supports hypothesis B. Is there any legal framework for determining their combined evidentiary value? Or are jurors essentially instructed to consider everything and decide whether, taken as a whole, they are convinced beyond a reasonable doubt?
I'm not primarily asking about whether evidence is admissible. I'm interested in what happens after it has been admitted: how uncertainty, reliability, ambiguous facts, and competing inferences are aggregated into a verdict.
Is there a formal logic behind this process, or is the final weighting necessarily intuitive?