What is jury nullification? It's when the jury acquits the defendant for reasons of their own. It's when the jury pretty much disregards the jury instructions and considers what they think should happen. Ethically, a lawyer is to not encourage this behavior. However, some attorneys have this thought in the back of their mind. Alas, jurors often make interesting decisions at trial, for odd reasons all the time jury deliberations.
The following article addresses some interesting legal jury nullification issues.