One concept that seems to boggle the minds of students learning about the common law jury system is jury nullification. As students have learned, generally this is the principle whereby jurors may ignore the law when reaching their verdict if they believe in good conscience that applying the law strictly in a case would be unjust. As I repeatedly tell students, most jurors have no idea that they have such power, and no judge in his or her right mind would instruct the jury about this right.
But would happen if a private citizen tried to inform potential jurors of this right on their way into the courthouse? Could that be considered tampering with the judicial system? Illegal? It should be, argued New York prosecutors in a case they brought against an 80 year old retired professor who stood outside courthouses and distributed information to people about jury nullification. See here for the result.