In 1930 the Polish medium Stanisława P. was tested at the Institut Metapsychique in Paris. French psychical researcher Eugéne Osty suspected in the séance that Stanislawa had freed her hand from control. Secret flashlight photographs that were taken revealed that her hand was free and she had moved objects on the séance table. It was claimed by spiritualists that during a series of séances in 1930 the medium Eileen J. Garrett channeled secret information from the spirit of the Lieutenant Herbert Carmichael Irwin who had died in the R101 crash a few days before the séance. Researcher Melvin Harris who studied the case wrote that the information described in Garrett's séances were "either commonplace, easily absorbed bits and pieces, or plain gobblede-gook. The so-called secret information just doesn't exist."
Magicians have a long history of exposing the fraudulent methods of mediumship. Early debunkers included Chung Ling Soo, Henry Evans and Julien Proskauer. Later magicians to reveal fraud were Joseph Dunninger, Harry Houdini and Joseph Rinn. Rose Mackenberg, a private investigator who worked with Houdini during the 1920s, was among the most prominent debunkers of psychic fraud during the mid-20th century.
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.