Orin Kerr links to a story of a New York federal judge who, bucking long-standing precedent, is now holding that jurors need to be informed of mandatory sentencing guidelines prior to their determination of guilt and innocence. Kerr predicts the ruling will quickly be reversed, as it flies in the face of well-established precedent that's existed for a good 100 years. But that doesn't make the question any less interesting.
This is one of things where how we idealize jury deliberation runs headlong into how I imagine jury deliberation actually works. Ideally, the punishment bears no relevance to the question of guilt or innocence. They're separate questions. In reality, I'd imagine that jurors would be more willing to fall on the "guilty" side of that fuzzy reasonable doubt line where they think the punishment is not too harsh, and rule "not guilty" when the punishment feels strongly out of line with what they think is deserved. When that information is not present, the jurors don't just have a blank slate; they instead fill in their mental gaps with an assumption of what the punishment is that correlates to how severe they imagine the crime to be.
Where this ruling does implicate "idealized" jury functionality is in the realm of jury nullification. If one does believe that juries should be allowed to nullify because they view the underlying law as unjust, the sentencing range of the law is clearly relevant information. Many people who don't have a problem with drug criminalization per se still find gross injustice in the wildly overinflated sentences drug convictions bring. Knowledge of those guidelines could lead to more nullifications and potentially reform of the law.