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.[178] 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.[179]
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.[84] 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.[85] 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.[86]