I served on a jury once for a theft case. It was really interesting. The case took about 4 days to hear all the testimony. Many of us jurors had lunch together each day, but we were instructed not to discuss the case. After 4 days of lunch, we hit the jury room and picked a foreman. Then, for the first time, we got to talk about the case.
WOW, it was like suddenly they were all different people. The foreman we picked turned out to have virtually no logical skills at all. He was useless - he wanted to base the entire case on believing the defendant's girlfriend over all the other witnesses. I think we picked him as foreman because he wore a tie each day and was well groomed. One guy immediately wanted to convict solely on his impressions of how the defendant looked. One guy wanted to throw out all the evidence because all the witnesses might be lying. The only guy on the whole jury I respected was a guy in a wheelchair who actually had logical facilities... he really put the guy who wanted to base things on the defendant's appearance in his place.
Ultimately we decided to convict. It took 3 days and was really tough.