Scottish born Helen Duncan was one of the most controversial materialization mediums of this century. Born in 1898, she rose to fame among the devout spiritualists specializing in the materialization of ectoplasm in forms recognizable by the sitters at her seances.
 
Mrs Duncan has the dubious distinction of being the last person to be prosecuted under the Witchcraft Act of 1735 (subsequently replaced by the Fraudulent Mediums Act in 1951), for regurgitating butter muslin at a seance and claiming it to be ectoplasm. She was sentenced to nine months in Holloway prison. The trial generated enormous interest and many witnesses testified that she was a genuine medium, among them Hannen Swaffer, a dedicated spiritualist, who was contemptuous of the allegations, and J.W. Herries, the chief reporter of the Scotsman, who claimed to have seen Mrs Duncan materialize the spirit of the late Sir Arthur Conan Doyle. Even a doctor gave evidence together with an X-ray of her stomach to show that the accusation could not be substantiated.

The police evidently kept an eye on Mrs Duncan and at a seance held in Nottingham in 1956 she was again harrassed. Although nothing incriminating was found, Mrs Duncan suffered severe shock and burns to her stomach. Spiritualists believe that the rapid withdrawal of ectoplasm into her body resulted in the physical injury and mental trauma. Six weeks later Mrs Duncan was dead, but the controversy lives on.
 

Comment and further reading:
 
See under Eva C.; and Florence Cook.