In 1988, the magician Bob Couttie criticized the paranormal author Brian Inglis for deliberately ignoring evidence of fraud in mediumship. Couttie wrote Inglis had not familiarized himself with magician techniques. In 1990 the researcher Gordon Stein discovered that the levitation photograph of the medium Carmine Mirabelli was fraudulent. The photograph was a trick as there were signs of chemical retouching under Mirabelli's feet. The retouching showed that Mirabelli was not levitating but was standing on a ladder which was erased from the photograph.
In 1880 the American stage mentalist Washington Irving Bishop published a book revealing how mediums would use secret codes as the trick for their clairvoyant readings. The Seybert Commission was a group of faculty at the University of Pennsylvania who in 1884–1887 exposed fraudulent mediums such as Pierre L. O. A. Keeler and Henry Slade. The Fox sisters confessed to fraud in 1888. Margaret Fox revealed that she and her sister had produced the "spirit" rappings by cracking their toe joints.