Mary Warren's role in the trials is not static. When the trials begin, she offers testimony that leads to the arrest and prosecution of Salem citizens; a notable example is what she tells the Proctors in Act II about her role in Goody Good's trial. Mary claims that Goody Good "nearly choked us all to death" when "she sent her spirit out." Mary goes on to relate her own experience with Goody Good mumbling at her when Mary refused her a cup of cider, claiming that she later became ill and implying that Goody Good had put a curse on her.
After Elizabeth Proctor's arrest, Mary briefly tries to come clean to the court about pretending to see spirits. She has the opportunity to bring the trials to a halt, but she is too fearful of the legal consequences of her deception, to say nothing of her fear that Abigail will kill her, as she has threatened to do. Ultimately, Mary returns to the side of the accusing girls and not only allows Elizabeth's conviction to stand, but implicates John Proctor, as well. Mary's moral weakness makes her one of the most reprehensible of the teen accusers.