Anna Margarethe Zwanziger (1760-1811) was a poisoner whose choice of poison was the popular arsenic to do away with her victims. She called arsenic ‘her truest friend’. Frau Glaser, her employer’s wife, had only recently returned to her husband’s house after a separation. She was dead within weeks. Anna went to work for Justice Grohmann, a somewhat sickly man of 38. Anna nursed him through several bouts of sickness and diarrhoea – she was, apparently devoted to him and grief-stricken after his death from yet another prolonged episode.
Her next post was at the house of Frau Gebhard who gave birth to a daughter on May 13th, 1809. Within days, Frau Gebhard was suffering from vomiting and diarrhoea. She was dead by May 20th. During the next months, guests and servants in the Gebhard household were taken ill. Anna was dismissed, but managed to poison two maids and the baby which died. Anna was arrested and was executed by the sword after confessing.
Feuerbach, the Bavarian judge, said that ‘Her attachment to poison was based on the proud consciousness of possessing a power which enabled her to break through every restraint, to attain every object, to gratify every inclination, to determine the very existence of others.’
Anna Zwanziger’s murderous career is described by Catherine Crowe in her 1850 book Light and Darkness which is the third volume of her series The Mysteries of Life. Catherine Crowe contributed articles to Household Words and Dickens had reviewed her work The Night Side of Nature or Ghosts and Ghost-Seers in 1848. Given his interest in murder and arsenic, it is not unreasonable to speculate that Dickens read her 1850 work.