Wikipedia

I will tell you what the jury orientation movie said (in San Francisco Superior Court), The jury is the last line of defense against injustice.

And that tells me (juxtaposed to Blackstone's ratio) that jury nullification is a duty if the law seems unfair, if the sentence may be too harsh or too cruel, if the standard of proof is too low, or if the rights of the defendant were unduly violated by law enforcement, the prosecution or the court (say, hacking the defendant's phone without a specific warrant, or using an IMSI catcher to locate the phone without a signed court order in advance).

Or if there's already evidence of miscarriage of justice, such as law enforcement officers lying in court in an effort to secure the conviction.

In the US our courts are already corrupt like nano SD cards, and they go through great lengths to choose jurors who will give them a blanket conviction without consideration of the fairness of the law. And yet if jurors are the last line of defense then it means it's their responsibility to make sure no unreasonable law is upheld, to assure that no-one is sent into the (squalid, abusive) prison industrial complex if the wrongdoing doesn't warrant such cruelty.