Uniqueness of the actual "prints" probably isn't even the main issue (with any biometrics). An imperfect or partial biometric "print" from a crime scene could "match" several originals regardless of whether the originals are unique.

In fact, this was used as an excuse by the FBI experts (after the exposure of their "mistake") for the incorrect match in the Madrid bombing. Of course if they had been competent (or honest?) they would have admitted upfront that a positive match could not be made with certainty because of the (lack of) quality of the print provided.