Just ask any JW about organ transplants, that will prove who they follow. Then ask what the consequences of not follwing the FDS's direction would be.
Sample presentation:
You: Good morning, how are you today? I was in your area performing a public service. I am eager to ask your viewpoint on a matter.
JW: householder: Oh, yes please.
You: Would you agree that Christians have a responsibility to follow the teachings of Christ Jesus found in the Bible?
JW: Definitely!
You: Glad to hear it! Did you know that many people have died refusing medical procedures like organ transplants, all because their religious leaders forbid them, even though there is no scriptural basis for such a prohibition?
JW: I have never heard of such a thing!
You: If you were faced with a loved one in need of a transplant, what would you do? Would you obey men above God's word!? Would you allow a family member to die because of human thinking?
JW: Never!
You: ( Hand them the article banning organ transplants, then ask..) If you had lived during this period of history when the WTBTS forbid organ transplants, what would YOU have done? Would you have obeyed the commands of men who had no scriptural backing for those commands?
JW: I uhhh, errr, mmmm, I trust the " faithful slave!"
You: More than God's word?
JW: I would never disobey the FDS..
You: What would happen if you did?
JW: I wouldn't.. but you could be DF'd.
You: For not following an idea of men?
JW: They are THE channel god is using. I would obey, we have the resurrection hope.
You: You don't have to die. There is no command against organ transplants. The GB expect you to obey, correct? They require that you obey them, correct?
JW: Yes.. I would just go along with whatever they say, even if it's wrong.
You: According to scripture, what kind of men expect others to follow them instead of God or Christ? What men want followers for themselves...??
JW: I, I, I, I, uh, uh, ermm, ( cough, cough..gasp! ) GyAHHHH!!!!!!
( Based on actual events )