I have had the occasion to encounter some JWs in my workplace. DF'd, and therefore expelled for some manner of "wrongdoing", but claiming to be JWs nonetheless. They still are adamant about not wanting blood or blood products. I believe that these people believe that the act of martyrdom - dying for the cause - will somehow expunge them of their "sins" and merit their resurrection in paradise.
Things like fornication and adultery and smoking aren't considered to be as much of a big "sin" as accepting a blood transfusion - those things can be "fixed" more or less - you can say you're sorry, you can make amends. But if you take a blood transfusion, it's an admission that you don't really believe that you'll be resurrected if you die. If you die after taking a blood transfusion, you're screwed for all eternity. If you die from refusing a blood transfusion, even if you're DF'd, you at least have a chance of coming back.