The justice system is undeniably flawed. What are your experiences with it as a juror?

I'm 30 and I have been called to jury duty six times and have served on a jury three times.

1st time- Domestic Violence - One of their children called the police. Wife denied abuse, Husband found not guilty.

2nd time- Drug Distribution - Man sold rock cocaine to an undercover cop. We found him guilty based almost entirely on the testimony of the undercover cop as the guy ditched the money and drugs before he was arrested. I learned a lot about rock cocaine.

3rd time- Assault and Battery - A girl was cheating on her boyfriend, whom she lived with, with one of her co-workers. The boyfriend found out and sent the girl to his parents house while he cooled off. Several days later the boyfriend attacked three guys as they left the co-workers apartment. He sucker-punched the first guy, then began brawling with the second two. The first guy began to have seizures so his two friends stopped fighting to help him and the boyfriend took off. The boyfriend immediately called the girlfriend, there were extensive phone records from the cell phone towers on his proximity to the scene of the crime. The other guy ended up being taken to the hospital in an ambulance and had a concussion and his face was messed up. Poor guy was just a friend of the co-worker he didn't have anything to do with the mess. They were all in their early twenties, watching them testify was like watching a train wreck. And the boyfriend was still with the girlfriend. It seemed like an open and shut case to me. Never count on other people's common sense. We deliberated for four days, all of the testimony was reread by the poor court reporter. Three people would not find him guilty, another guy would change his vote just to hear himself talk. It was insanely frustrating. The jury was hung and the case went on to be retried.

Pro-tip: Don't call anyone while fleeing the scene of a crime, they really can track you.

TL;DR - Common sense is your friend.