The Austrian medium Rudi Schneider was investigated in 1924 by the physicists Stefan Meyer and Karl Przibram. They caught Rudi freeing his arm in a series of séances. Rudi claimed he could levitate objects but according to Harry Price a photograph taken on April 28, 1932 showed that Rudi had managed to free his arm to move a handkerchief from the table. According to Warren Jay Vinton, Schneider was an expert at freeing himself from control in the séance room. Oliver Gatty and Theodore Besterman who tested Schneider concluded that in their tests there was "no good evidence that Rudi Schneider possesses supernormal powers."
^ Paul Kurtz. (1985). A Skeptic's Handbook of Parapsychology. Prometheus Books. p. 29. ISBN 978-0-87975-300-9 "Florence Cook was caught cheating not only before her séances with Crookes but also afterward. Furthermore, she learned her trade from the mediums Frank Herne and Charles Williams, who were notorious for their cheating." Also see M. Lamar Keene. (1997). The Psychic Mafia. Prometheus Books. p. 64. ISBN 978-1-57392-161-9 "The most famous of materialization mediums, Florence Cook – though she managed to convince a scientist, Sir William Crookes, that she was genuine – was repeatedly exposed in fraud. Florence had been trained in the arts of the séance by Frank Herne, a well-known physical medium whose materializations were grabbed on more than one occasion and found to be the medium himself."
The psychologist and psychical researcher Stanley LeFevre Krebs had exposed the Bangs Sisters as frauds. During a séance he employed a hidden mirror and caught them tampering with a letter in an envelope and writing a reply in it under the table which they would pretend a spirit had written. The British materialization medium Rosina Mary Showers was caught in many fraudulent séances throughout her career. In 1874 during a séance with Edward William Cox a sitter looked into the cabinet and seized the spirit, the headdress fell off and was revealed to be Showers.
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.
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.
The trance medium Leonora Piper was investigated by psychical researchers and psychologists in the late 19th and early 20th century. In an experiment to test if Piper's "spirit" controls were purely fictitious the psychologist G. Stanley Hall invented a niece called Bessie Beals and asked Piper's 'control' to get in touch with it. Bessie appeared, answered questions and accepted Hall as her uncle. The psychologist Joseph Jastrow wrote that Piper pretended to be controlled by spirits and fell into simple and logical traps from her comments. Science writer Martin Gardner concluded Piper was a cold reader that would "fish" for information from her séance sitters. The physiologist Ivor Lloyd Tuckett who examined Piper's mediumship in detail wrote it could be explained by "muscle-reading, fishing, guessing, hints obtained in the sitting, knowledge surreptitiously obtained, knowledge acquired in the interval between sittings and lastly, facts already within Mrs. Piper's knowledge." https://drive.google.com/file/d/1v-yKnSyHSOKG16JAd6WMkAyRH9zcHZJe/view?usp=sharing
Modern spiritualists and psychics keep detailed files on their victims. As might be expected, these files can be very valuable and are often passed on from one medium or psychic to another when one retires or dies. Even if a psychic doesn't use a private detective or have immediate access to driver's license records and such, there is still a very powerful technique that will allow the psychic to convince people that the psychic knows all about them, their problems, and their deep personal secrets, fears, and desires. The technique is called cold reading and is probably as old as charlatanism itself... If John Edward (or any of the other self-proclaimed speakers with the dead) really could communicate with the dead, it would be a trivial matter to prove it. All that would be necessary would be for him to contact any of the thousands of missing persons who are presumed dead—famous (e.g., Jimmy Hoffa, Judge Crater) or otherwise—and correctly report where the body is. Of course, this is never done. All we get, instead, are platitudes to the effect that Aunt Millie, who liked green plates, is happy on the other side.
A very large part is played by fraud in spiritualistic practices, both in the physical and psychical, or automatic, phenomena, but especially in the former. The frequency with which mediums have been convicted of fraud has, indeed, induced many people to abandon the study of psychical research, judging the whole bulk of the phenomena to be fraudulently produced. https://drive.google.com/file/d/1RFGELbyuulzukp4fF5oNPvw1piXNw33d/view?usp=sharing
A widely known channeler of this variety is J. Z. Knight, who claims to channel the spirit of Ramtha, a 30 thousand-year-old man. Others purport to channel spirits from "future dimensions", ascended masters, or, in the case of the trance mediums of the Brahma Kumaris, God. Other notable channels are Jane Roberts for Seth, Esther Hicks for Abraham, and Carla L. Rueckert for Ra.
In the later half of the 20th century, Western mediumship developed in two different ways. One type involved clairaudience or sensitives who hear spirit, and then relay what they hear to their clients. The other incarnation of non-physical mediumship is a form of channeling in which the channeler goes into a trance, or "leaves their body", allowing a spirit entity to borrow their body, who then speaks through them. When in a trance the medium appears to come under the control of the spirit of a departed soul, sometimes entering into a cataleptic state, although modern channelers may not. Some channelers open the eyes when channeling, and remain able to walk and behave normally. The rhythm and the intonation of the voice may also change completely.