Final answer:
In Act 3 of 'The Crucible', Deputy Governor Danforth accuses Mary Warren of committing perjury, indicating a serious crime of lying under oath during the witch trials.
Step-by-step explanation:
In Act 3 of The Crucible, Deputy Governor Danforth asserts that Mary Warren has committed perjury, which is the act of lying under oath in a court of law. Danforth believes that Mary's recantation of her previous testimony, in which she accused individuals of witchcraft, is a lie, pointing to this as an act of deception. Given Salem's theocratic society and the intense fear of witchcraft, perjury here is treated as a severe crime, and Mary's actions disrupt the court and undermine its authority, leading Danforth to react sternly against her.