In the movie Twelve Angry Men, how well does the group deal with its participation problems?
A good approach would be to identify the participation problems first, then address they ways in which the group deals with them.
For example, one problem is that some jurors want to deliver a verdict and get out so they can get on with their lives. They think more about things they might miss (like a baseball game) than about the issue at hand. Ask yourself, "How do the other characters deal with these men?" Are they able to get these men to focus on the task at hand? Once you answer that question, you'll know if the group deals with the problem "well".
What other problems come up in the course of the deliberation? Are there problems of bias/prejudice? Emotional investment? Ignorance? Short-sightedness? Lack of analysis?