It was once popularly believed that Shiel had spent time in prison for fraud. However, it was discovered in 2008 that in 1914 Shiel had actually been convicted under the Criminal Law Amendment Act (1885) for "indecently assaulting and carnally knowing" his 12-year-old "de facto" stepdaughter. Unrepentant, Shiel served sixteen months hard labour in prison, complaining to the Home Secretary about the law, though he assured his publisher Grant Richards in a letter that he had been treated well. Shiel's discussion of his crime is disingenuous; he conceals from Richards the identity of his victim in addition to misleading him about her age. Instead he refers to "love-toyings" with an older girl on the cusp of maturity. Nor does Shiel mention that he had known both the girl and her mother's sisters long before his conviction, perhaps intimately, as contemporary letters from one of the sisters to Shiel suggest. Court records described Shiel as a "clerk and metal worker"; one of the witnesses was a metal worker and the records may have transposed some information. He appealed the conviction unsuccessfully.