[2] She confessed to having been a witch and that her familiar was a cat (later turned into a toad) by the name of Sathan (which is just an obsolete variant for satan), which originally belonged to Elizabeth Francis.
[2][3] Agnes was put on trial in Chelmsford, Essex, England, in 1566 for using witchcraft to cause illness to William Fynne, who died on 1 November 1565.
Information from the trial of Agnes Waterhouse is recorded in a pamphlet from 1566 titled, "The examination and confession of certaine Wytches at Chensforde in the Countie of Essex before the Quenes Maiesties Judges the XXVI daye of July anno 1566.
Elizabeth Francis received the cat from her grandmother, Mother Eve of Hatfield Peverell, who taught her witchcraft when she was twelve years old.
She confessed to stealing sheep, and killing several people including a wealthy man, Andrew Byles, who would not marry her after she became pregnant with his child.
She reportedly taught her how to perform witchcraft as she was instructed before by her grandmother, Mother Eve, telling her that "she must call him Satan and give him of her blood and milk as before.
Joan Waterhouse had been refused a piece of bread and cheese by a neighbour's child, Agnes Brown, and had invoked the toad's help.
[6] Joan Waterhouse did not claim to have used the supernatural services of the cat to any large degree, but by testifying to its existence, helped convict the other two women.
[6] In her testimony, Agnes Brown described the demon as a black dog with a face like an ape, a short tail, a chain and a silver whistle around his neck, and a pair of horns on his head.
[8] Agnes Waterhouse is a featured figure on Judy Chicago's installation piece The Dinner Party, being represented as one of the 999 names on the Heritage Floor.