LogFAQs > #968114473

The question of Deckard's humanity is left purposely ambiguous, IMO. It is true there are hints that he could be a Replicant, such as Gaff leaving behind an origami unicorn from Deckard's dream and Deckard's eyes having the telltale Replicant retinal glint in one scene.

Nevertheless, I do not feel these were ever intended to be taken to their logical conclusion (i.e., that he is a Replicant). Roy's mercy and death spell out the theme for the audience. Deckard's humanity (or plausible lack thereof) is best left as a subtextual adjunct to the overall message. To reiterate what someone else said, not so much "is he or isn't he?" But rather "does it really matter?"