Jury nullification is the term to search for here. I'd really recommend you just dive in and do your own reading. Its a complex topic that is viewed very poorly by lawyers and judges, not surprisingly as it means the success of their cases depend on juries that may not necessarily be predictable.

The history of this is fascinating though as it goes right back to the founding of the US and why our legal system is designed the way that it is. I know one of the founders wrote extensively on this I want to say it was John Adams but then I'm sure Hamilton did as well since the dude never stopped writing.