Group discussion is hindered for a variety of reasons, one being each juror's bias and the lack of respect for the jury process. The majority of men are eager to declare the guilty verdict and be on their way, especially on an incredibly hot day. Juror 8 is the only man that wants to discuss the case, testimony, and really study whether or not there is or is not reasonable doubt. He outrages jurors 3 and 10 by being the only one to vote 'not guilty' and force everyone to discuss the matter.
Remember, all twelve men are VERY different; you need to consider age, background, occupation, and overall personality. Reginald Rose does an amazing job of giving readers clues about each juror within their dialogue. Prejudices and bias cause lack of communication and heated arguments. Many men assume the boy's guilt because of the background information provided. He is a "bad kid" from a "bad neighborhood" so therefore he killed his father. Jurors 3 and 10 feel so confident in this mindset that they refuse to listen to reasoning from Juror 8 and eventually others as the vote begins to more toward 'not guilty.' Juror 8's persistence, level-headed way of talking, and lack of bias allows more room for discussion and the eventual decision.
There are many obstacles to communication in the play. The men have different ideas about the role of the jury, so there is disagreement on that issue from the beginning. Some of the men, such as the one who wants to attend the baseball game, are in a hurry to leave. The chairman, who attempts to organize the discussion, is a rather weak individual whom the men do not seem to respect. Also, the men are from different ethnic groups, different socio-economic groups, and different professions. For the most part, each brings different kinds of prejudices to the jury room. As you read or listen to each juror, you will see that each has viewed the testimony and the witnesses through a different "lens," with one juror noticing one point, and another juror missing that point completely. All in all, it is difficult to put twelve strangers with nothing in common in one room and expect them to begin a group discussion that is a matter of life and death. Yet somehow, the miracle of the jury is that this is accomplished most of the time!