In addition to what the sibling commenter said about extra approval, also consider that in many places the prospective jurors is told up-front that the death pe

In addition to what the sibling commenter said about extra approval, also consider that in many places the prospective jurors is told up-front that the death penalty is on the table, and jury candidates who are not ok with that are dismissed. So I'd expect that if possible punishments weren't discussed beforehand, you'd end up with a jury that doesn't support the death penalty quite as much. And in that jury you'd be more likely to find someone who might believe the defendant is guilty, but vote to acquit because they don't believe their crime merits death, but are pretty sure that that's what the sentence would end up being if convicted. And in that jury you might even find someone who is opposed to the death penalty entirely, and vote to acquit for the same reasons.