Identify specific moments in the play that show that when hysteria and fear take over, the truth is lost.
I think that you can find a specific moment of fear and hysteria overwhelming the truth at the end of Act I. The onslaught of accusations that happen with such ferocity and full force at the end of the first act is a recognition of the fear that has come to dominate Salem. Hysteria and fear have overcome people in the setting. Tituba is a prime example. Struck and paralyzed by fear and hysteria of what is happening and the forceful nature of her abandonment, she gives in to false positive identifications, if only to experience power in her own right. At the same time, the accusations that begin at this point are motivated by the need to deflect attention and force it on someone else, indicating how that truth has become misplaced in a such a setting.
Another instance of hysteria and fear overtaking an individual and causing truth to be misplaced as a result would be during the trials to end Act III. Proctor is convinced that if Mary Warren breaks ranks and testifies against Abigail and the other girls, the truth will emerge. For her part, Abigail organizes an inclusion that crushes Mary's will, and compels her to recognize that hysteria and fear that overcomes her at the prospect of being alone and cut off from others. In this, Mary puts aside truth. She blames Proctor and names him as the devil, if only because she is gripped by hysteria and fear in being alone from others. In these two examples one can see how Miller represents some of the very worst, and perhaps sadly true, elements of human nature in articulating how hysteria and fear can easily cause the truth to be put aside.