The primary support for John's claim is the incident of the poppet found in the Proctors' household. The little doll belongs to Elizabeth, and when questioned, she does not hesitate to claim it because she is innocent of any wrongdoing. However, a needle is found in the poppet, evidence to those in the drama that Elizabeth had been practicing witchcraft, stabbing the poppet to cause pain for someone she wished to harm.
Elizabeth, however, had not pushed the needle into the poppet; Abigail Williams had done it to incriminate Elizabeth, to see that she is condemned and executed. Abigail hates Elizabeth and wants John Proctor for herself, even though he ended their affair. John knows this, and Mary Warren, when she is telling the truth, confirms that Abigail is misleading the court. John tells the court that vengeance is afoot in Salem, but his protests are ignored.
It was mary warren, not elizabeth.