What do Jurors #12 and #3 do to make #8 upset?

Both Jurors 12 and 3 start drawing diagrams that are not necessarily accurate or useful. Juror 8 thinks they are playing games:

(Cut to close shot of TWELVE who doodles a picture of an el train on a scrap of paper.)

THREE. Well, what have you got to say about that?

EIGHT. I don’t know. It doesn’t sound right to me. THREE.

Well, supposing you think about it. (To TWELVE) Lend me your pencil. (TWELVE gives it to him. He draws a tick-tack-toe square on the same sheet of paper on which TWELVE has drawn the train. He fills in an X, hands the pencil to TWELVE.)

THREE. Your turn. We might as well pass the time. (TWELVE takes the pencil. EIGHT stands up and snatches the paper away. THREE leaps up.)

THREE. Wait a minute! EIGHT (hard).

This isn’t a game.