The medium Frank Decker was exposed as a fraud in 1932. A magician and séance sitter who called himself M. Taylor presented a mail bag and Decker agreed to lock himself inside it. During the séance objects were moved around the room and it was claimed spirits had released Decker from the bag. It was later discovered to have been a trick as Martin Sunshine, a magic dealer admitted that he sold Decker a trick mail bag, such as stage escapologists use, and had acted as the medium's confederate by pretending to be M. Taylor, a magician. The British medium Estelle Roberts claimed to materialize an Indian spirit guide called "Red Cloud". Researcher Melvin Harris who examined some photographs of Red Cloud wrote the face was the same as Roberts and she had dressed up in a feathered war-bonnet.
Spiritualists believe that phenomena produced by mediums (both mental and physical mediumship) are the result of external spirit agencies. The psychical researcher Thomson Jay Hudson in The Law of Psychic Phenomena (1892) and Théodore Flournoy in his book Spiritism and Psychology (1911) wrote that all kinds of mediumship could be explained by suggestion and telepathy from the medium and that there was no evidence for the spirit hypothesis. The idea of mediumship being explained by telepathy was later merged into the "super-ESP" hypothesis of mediumship which is currently advocated by some parapsychologists.
Most working mediums are not fully developed most are clairsentient they can only sense and see spirit within the third eye all these working mediums want to be clairvoyant so again only go with your gut feeling when joining a circle, no one needs to tell you are a medium you know within yourself, your guides will help you to a development circle where the medium is humble and helpful teacher.
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.
The exposures of fraudulent activity led to a rapid decline in ectoplasm and materialization séances. Investigator Joe Nickell has written that modern self-proclaimed mediums like John Edward, Sylvia Browne, Rosemary Altea and James Van Praagh are avoiding the Victorian tradition of dark rooms, spirit handwriting and flying tambourines as these methods risk exposure. They instead use "mental mediumship" tactics like cold reading or gleaning information from sitters before hand (hot reading). Group readings also improve hits by making general statements with conviction, which will fit at least one person in the audience. Shows are carefully edited before airing to show only what appears to be hits and removing anything that does not reflect well on the medium.
In the late 1920s and early 1930s there were around one quarter of a million practising Spiritualists and some two thousand Spiritualist societies in the UK in addition to flourishing microcultures of platform mediumship and 'home circles'. Spiritualism continues to be practised, primarily through various denominational Spiritualist churches in the United States, Canada, Australia and the United Kingdom. In the United Kingdom, over 340 Spiritualist churches and centres open their doors to the public and free demonstrations of mediumship are regularly performed.