Sherlock Holmes: 60 for 60

I think that's a good theory, especially in conjunction with thesmallhobbit's point about how ACD may have just used the Mormons because they were convenient and exotic. Clearly they were known, based on the trial, and I have no doubt that the newspapers at the time sensationalized the trial as much as possible (ah, yellow journalism, long may you live). They would have been a natural villain, particularly for the tale that ACD wanted to tell of revenge and love lost.