That's because it's not legal. It's a violation of the jury's duty to render a verdict based on the law and the facts presented. Stating an intention to vote a certain way without respect to the law and facts is grounds for removal from the jury. See https://www.law.cornell.edu/wex/jury_nullification and the referenced court case.
It's a violation of the jury's duty to render a verdict based on the law and the facts presented.
Who assigned the jury that duty? And when did that happen?
Per http://law2.umkc.edu/faculty/projects/ftrials/zenger/nullifi... and other sources that I have seen, the understanding of the law when the Constitution was written was that juries should judge both the law and the facts. The view that they should not judge the law only arose decades later in the late 1800s. The fact that the legal profession today sees jurors as having a duty to NOT judge the law I see as undermining the intent of having jury trials in the first place.
The understanding of jury trials when the Constitution was written was that juries had a right and obligation to judge both the law and the facts. The first laws
However, jury verdicts of acquittal are unassailable even where the verdict is inconsistent with the weight of the evidence and instruction of the law.
