Chalk this up as an unintended side effect of recycling proliferation:Forensic technology developed for use on virgin plastics is now being foiled by products made from recycled polymers, making it much more difficult to lift fingerprints off of plastic surfaces. This is forcing law enforcement officials to effectively rewrite the book in dealing with plastics.

While traditional plastics might contain only one or two chemical building blocks, the structures of plastics containing even a small percentage of recycled material are far more byzantine. It is hoped that new developments by forensic chemists at agencies such as the Home Office Scientific Development Branch in the U.K. will help overcome some of the challenges presented by these new plastics.

None of which serves to explain just who the Hell stole my bottle of Fresca?
SOURCE: New Scientist