“The trier of fact, in this case the jury, decides what facts are worthy of belief and weight, and their findings won’t be overturned on appeal abuse of discretion, proof of prosecutorial misconduct (concealing evidence from the defense) or newly discovered evidence. Since the defense knew about the evidence but couldn’t get it in, it won’t enter into the court’s decision absent the above abuse of discretion.”
If it was not entered into evidence, the jury did not hear it to weigh it.
Yes, that’s precisely the point: if the appellate court decides that the judge improperly excluded evidence that would have made a difference in whether the jury found them guilty, the appellate court could find the judge abused his discretion and send the case back for another jury trial.
They could also find he abused his discretion but that it was “harmless error”: that it wouldn’t have made a difference. in which case there’s no new trial and the verdict stands as is.
NOTE: the above is an explanation of procedure, not a defense of “the evil justice system”.