An illiterate American orphan girl who was instrumental in arousing lively interest in Spiritualism in Ohio soon after the phenomenon of the Rochester Rappings. Mrs. Kellogg of Massillon, in whose house Warner performed domestic services, discovered that raps were produced in the girl's presence. Soon she was able to move into a trance state, and the un-educated girl, who at eighteen could only read printed characters, wrote with both hands at the same time on different subjects, while a third communication was spelled out by raps.
Reports of the séances began to be widely circulated. Abel Underhill, a physician, took the girl into his family for medical treatment and wrote her history. The occurrences at St. Timothy's Church on Christmas Eve, 1851, put her in the limelight. Supposedly, unusually powerful raps resounded in the church in her presence and attracted the attention of the whole assembly. The minister asked that "those knockings might cease." Instead, they increased in vehemence.
Warner was arrested on a charge of disturbing a religious meeting and brought before a public tribunal. The trial commenced on December 27 and lasted for three days. As "not a single witness could be found who could swear that they perceived the slightest movement in the accused party; on the contrary, when closely examined, those who professed to have scrutinized the action of the spirit rapper narrowly were compelled to admit that they could not detect the least perceptible motion, even of her dress, at the times when the knocks were most numerous and emphatic," the defendant was discharged.
Following the acquittal, Underhill announced an investigation by a selected committee, under stringent test conditions, of the medium's physical and mental phenomena. Four séances were held. The committee believed the phenomena wholly unaccountable and genuine evidences of an occult and intelligent force outside the medium.