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Mathematics Goes to the Movies

by Burkard Polster and Marty Ross


12 Angry Men (1957)

MEMBER OF JURY: Are you trying to tell me that this knife really fell through a hole in the boy's pocket, someone picked it up off the street, went to the boy's house and stabbed his father with it just to test its sharpness?
DAVIS: No, I’m just saying that it's possible the boy lost his knife and somebody else stabbed his father with a similar knife. It’s just possible.
MEMBER OF JURY: Take a look at this knife. It's a very unusual knife. I've never seen one like it. Neither had the storekeeper who sold it to the boy. Aren't you asking us to accept an incredible coincidence?
DAVIS: I'm just saying a coincidence is possible.
MEMBER OF JURY: And I say it's not possible. (Davis produces an identical knife)
MEMBER OF JURY: Where did that come from?
MEMBER OF JURY: It's the same knife!
MEMBER OF JURY: What do you think you're doin'?
MEMBER OF JURY: Where did you get it?
DAVIS: I went out walking for a couple of hours last night. I walked through the boy's neighbourhood. I bought that at a little pawn shop just two blocks from the boy's house. It cost six dollars.
MEMBER OF JURY: It's against the law to buy or sell switchblade knives.
DAVIS: That's right. I broke the law.
MEMBER OF JURY: You pulled a real bright trick. Now supposing you tell me what it proves. Maybe there are ten knives like that. So what?
DAVIS: Maybe there are!
MEMBER OF JURY: What does it mean? You found another odd knife like it. What's that? The discovery of the age, or something?
MEMBER OF JURY: I mean, you are asking us to believe that somebody else did the stabbing with exactly the same kind of knife?
MEMBER OF JURY: The odds are a million to one.
MEMBER OF JURY: DAVIS: It's possible!
MEMBER OF JURY: But not very probable.
MEMBER OF JURY: OK, fellas. Let's take our seats.