A better conception of evidence is this:
A fact X is evidence that a theory Y is true if and only if Theory Y being true makes Fact X more likely to have happened
relative to the case where Theory Y is false.
Consider this case: There was a robbery in Queens. Suspect Hockney was spotted in Queens the night of the crime. Is the fact that Hockney was spotted in Queens evidence that Hockney committed the robbery? In this case, no, it's not, because of some further information that came to light: it turns out Hockney lives in Queens. Since he lives there, it's
just as likely that he would be spotted there if he
did commit the robbery or if he
didn't commit the robbery.
We can also talk about the
strength of evidence, and conceptualize it as follows: the more likely Fact X is if Theory Y is true
relative to how likely Fact X is if Theory Y is false, the
stronger evidence Fact X is of Theory Y. In other words, Fact X doesn't have to be absolute proof of Theory Y to be useful evidence; it can be strong without being proof, or it can be weak but still at least somewhat persuasive. The stronger it is, the more we should be convinced.
Say there was a jewel heist, and the thief who took the diamond and escaped out the window left behind Size Ten footprints. The cops round up the usual suspects, and Suspect McManus turns out to wear Size Ten shoes. Is this evidence against him? Yes. If he
didn't steal the diamond (i.e. if Theory Y is false) then the chances that the thief would be someone who sore Size Tens (Fact X) would be, say, one in five, going on an estimate that one in five men wear Size Ten shoes. But if he
did steal the diamond (i.e. if Theory Y is true) then the chances that the thief would leave behind Size Ten footprints would be 100% since he would be the thief and that's his shoe size. That's a pretty big change in probability, from 20% to 100%.
But wait! That's not all there is to evaluating evidence. If the cops picked him up because he's one of a handful of well-known jewel thieves, that's one thing. But if the cops picked him up by flipping open the phone book and bringing in some random schmoe to check his shoe size, that's
something completely different. The shoe size is strong evidence against McManus but it's weak evidence against Joe Schmoe, because the probability of McManus being the thief is high and the probability of Joe Schmoe being the thief is very low,
before considering the shoe size evidence. Evidence operates on our
prior beliefs. If we already have reason to believe Theory Y is true even without Fact X, then Fact X can be enough to move us from somewhat convinced of Theory Y to strongly convinced of Theory Y. Whereas if we have little reason to believe Theory Y (how likely is it that a name literally chosen at random from the phone book is the one who stole the diamond?) then Fact X may do almost nothing whatsoever to make Theory Y more convincing (So what if he wears Size Tens?
Lots of guys wear Size Tens!).
My stance has been, and continues to be, that almost all of the facts leveled against Bobbi and her hypothetical conspirators are no more likely under the theory that they cheated than they are under the theory that they didn't cheat; they all have perfectly reasonable explanations that don't include cheating. Accordingly, they aren't evidence of cheating. And moreover, for any that
are more likely under the cheating theory than they are under the no-cheating theory, the strength of that evidence is weak and the prior probability of cheating is small, such that adding the weak evidence to an unlikely theory still leaves the theory unlikely.