Once, and I'll never forget it. It was a murder trial, but not whether the defendant committed the murder (of his girl friend). He did. It was about deciding the degree of the murder: Manslaughter (accident), Felony murder, or Murder 1 (premeditated).
The jury members were all over the place (vote 4-5-3). It was clear to me he was guilty of *at least* felony murder. He was illegally carrying the weapon at the time (a felony). We spent 5 hours in deliberation and ended agreeing on that, but it was rough going.
Later I met one of the jurors in a department store and he said he knew the man, and that he had killed another woman previously and got away with it. He should have been rejected as a juror. We were not supposed to know that. I didn't.
I think I was fair. He was probably guilty of Murder 1. The evidence just didn't support it conclusively, imo. I don't know what would have happened though if we had not agreed relatively soon, and the judge had refused let us quit.
Btw, it turned out the sentence was the same for the last two levels.