During jury selection the judge will ask if you deliver a guilty verdict if the defendant is guilty. When you say no, you're off the jury.

If you lie the judge will kick you off the jury when he figures out you're lying. He'll be angry, and he can fine or jail you if he wants to make a point.

I'm not sure jurors can be jailed. Do you have precedent for this?

A judge can absolutely jail you for contempt of court. And he pretty much gets to decide what that means. It's unlikely you'd get jailed for this kind of thing, but it's not impossible.

so, no precedent of a judge citing a juror for contempt, then?

Is Google really that hard to use? Did you think maybe you might look at the jury nullification wiki page?

Relevant: Doug Stanhope on Jury Duty (language NSFW):

https://www.youtube.com/watch?v=kp-5rvtSpak