Why does Reginald Rose make the foreman ineffective in Twelve Angry Men?

Making the jury foreman a weak and ineffective character
works to strengthen the theme of the play. In the American system of justice, a jury has
the duty to examine and weigh the evidence, without prejudice, and arrive at a just
verdict; it is the responsibility of the jury foreman to provide leadership and direct
deliberations so that the jury discharges its duties as they are legally and ethically
bound to accomplish them.

In making the jury foreman an
ineffective character, the playwright points to one flaw in the justice system that
would lead to grave injustice. Also, because the foreman is not doing his job, Juror
Eight, being a man of integrity, steps into the breach and becomes the leader among the
members of the jury. In doing this, he challenges the power structure in the room,
refusing to remain silent as an injustice occurs. The theme of the play develops from
the actions of Juror Eight: the American system of justice is only as fair as those who
participate in it, and when an injustice takes place, it is a person's moral
responsibility to step forward and oppose it.