In the novel Dumb Witness, Julia Tripp is one of two eccentric sisters and amateur spiritualists who share a home near Little Green House, in Market Basing.
Julia is described as being "nearer fifty than forty". She wears her hair "parted in the middle in Madonna fashion", and has brown eyes which are "slightly prominent".
Hastings observes that Julia and her sister Isabel are "vegetarians, theosophists, British Israelites, Christian Scientists, spiritualists and enthusiastic amateur photographers".
Julia tells Poirot that on the night Emily Arundell was taken ill, she and Isabel had gone to Little Green House, and had a sitting after dinner. She says that she, Isabel and Wilhelmina Lawson distinctly saw "a kind of halo" around Miss Arundell's head. She described it as a kind of luminous haze.
Julia also tells Poirot that they have had messages from Miss Arundell, saying that she was very happy, everything was beautiful, and that she hoped there was love and peace among her relatives.