Having served on a couple of juries I agree the jurors are there to make a legal finding: did the defendant break the law in the way the prosecution has charged them with doing.
However isn't a jury also supposed to render justice? Isn't our legal system founded on the principal that defendants are entitled to justice? Lawyers talk about runaway juries but it does happen that juries decide, "This law is just plain wrong," and acquit. Or decide, "Any reasonable person could have reacted the way the defendant did," and they acquit.
To my mind, for a jury to do that is not a miscarriage of justice, that IS justice.
And that reasoning leads to the juries deciding that the victim of the crime didn't deserve justice. Assaulted pedophile, who cares? You deserved it. There's a reason justice should be blind. Value judgements should be evaluated when sentencing not when determining if a crime happened. Justice is the end result of the process not a mid point.