addlegalhistorytothecourseofstudy
This has only partly to do with history of any kind.
You have the POWER to nullify. That is because you have the POWER to think one thing and say another. Without the laws I have referred to, someone might be able to interrogate you and discover that you are doing so. But they can't.
Since laws seem to exist, and didn't just come into existence by accident, that protect you from such interrogation (once an actual juror), and that license you to know the penalty faced by a defendant, somebody, somewhere who had some pull must think that you, as a juror, are there to use information other than simply the facts and are entitled to do this without government interference.
It hardly seems likely that the government would pass laws that hamstring itself, so they must have been hemmed in by that pesky constitution.
Find me someone who claims to know even only all of Title 18 US Code. I'll call him a liar and put $1000 down that I can prove I'm right. And that's just a small fraction of the laws available for the government to clobber you with. There's no way to know what they all are, so even an honest person can't avoid doing criminal acts every day.
That is an intolerable state of affairs.
Fact is, there are people who like to control others, and they manage to get their wishes into law on a regular basis. I will resist those people whenever I find the opportunity to do so, and jury nullification is a way to do it. And, as a bonus, whether you opine so or not, it is built into the system.
Not only that, it's built into the system because it cannot be kept out. Decent people seeing tyrrany being carried out will simply lie their way to an acquittal or a hung jury.
You can point to all the legal history you want. Precedents are for judges, not for jurors.
Jury nullification is going to happen for the same reason a dog licks its private parts. Because it can.