Poisoning the Well fallacy is when you make a statement that already shuts down any argument that your opponent might bring up
The character in Twelve Angry Men that used this fallacy was The Yankee.
The Yankee said “You can’t change my mind if you talked for 100 years”
By The Yankee saying this he committed a Poisoning the Well fallacy because he is saying that no matter what anyone in the room says he is not changing his vote. He is already saying that the arguments that anyone will say have been discredited because he has already made up his mind. Instead of saying this The Yankee should have said “I am pretty set on my decision of