The broad overall charge brought against Kit in chapter 19 of The Witch of Blackbird Pond is witchcraft and consorting with the devil.
"Katherine Tyler, thou art here accused that not having the fear of God before thine eyes thou hast had familiarity with Satan the grand enemy of God and man, and that by his instigation and help thou hast in a preternatural way afflicted and done harm to the bodies and estates of sundry of His Majesty's subjects, in the third year of His Majesty's reign, for which by the law of God and the law of the Colony thou deservest to die."
Specifically, Kit is accused of working with the devil to hurt the members of the town. Kit is accused of consorting with Hannah Tupper, whom the townsfolk believe is a witch. Kit supposedly learned witchcraft from Hannah. To make matters worse for Kit, the charges specify that Kit has been using her devil witchcraft powers to hurt the innocent children of the town. She supposedly makes them sick and die.
"Mistress Tyler, you are accused by Adam Gruff with the following actions. Firstly that you were the familiar friend and companion of the Widow Hannah Tupper of Blackbird Pond, an alleged witch who has within the past week disappeared in a suspicious manner. Such friendship is a lawful test of guilt, inasmuch as it is well known that witchcraft is an art that may be learned and conveyed from one person to another, and that it has often fallen out that a witch, upon dying, leaveth some heir to her witchcraft. "Secondly, that you are guilty of actions and works which infer a court with the devil, which have caused illness and death to fall upon many innocent children in this town."
Kit is then asked if she knows Hannah Tupper. Yes, she knows Hannah. Then Kit is asked if she has seen Hannah's cat. Yes to that one too. The next question asked of Kit is whether or not she has done some "enchantments" with Hannah. Kit replies no.
Kit proves her innocence with the help of Nat. Together they prove that Kit is not a witch because she helped Prudence learn to read the Bible.