Key features of the Spanish Prisoner are the emphasis on secrecy and the trust the confidence artist is placing in the mark not to reveal the prisoner's identity or situation. The confidence artist will often claim to have chosen the mark carefully based on his reputation for honesty and straight dealing, and may appear to structure the deal so that the confidence artist's ultimate share of the reward will be distributed voluntarily by the mark.
Modern variants of the Spanish Prisoner include the advance fee fraud, in which a valuable item must be ransomed from a warehouse, crooked customs agent, or lost baggage facility before the authorities or thieves recognize its value, and the Nigerian money transfer fraud, in which a self-proclaimed relative of a deposed African dictator offers to transfer millions of ill-gotten dollars into the bank account of the mark in return for small initial payments to cover bribes and other expenses.