Happenstance - S7-E8
Corrected entry: When they run fingerprints on the envelope from "Dora" they put the fingerprints from the left side and the right side of the envelope together to make one print from two partials but this would be impossible as one partial would be from the right thumb and one partial would be from the left thumb by the way the envelope is held.
Correction: If it had been held that way, sure. But there's nothing that says it was. It's possible the daughter held it with her left thumb in two different places, leaving two partials.
CocoCami