So really neither the fingerprint or whatsapp had anything to do with the arrest.
We think it’s this guy and we can match a small portion of his fingerprint with the picture.
Maybe it’s statistically significant beyond reasonable doubt but seems like a little too much of a stretch to me.
This is just building enough evidence to convict someone based on matching a photograph of a partial finger to a suspect's hand. Which sounds perfectly reasonable and legitimate (as legitimate as fingerprints can be). Just because there's not enough in the photo to match a national database doesn't mean there's not enough to be statistically certain it's a match with the suspect.
The article is light on details about how the fingerprint was actually used so one can only speculate. My assumption here though is that whatever they recovered wouldn’t stand up on its own but used in conjunction with other evidence it might have added to the case against the parties.
It’s hardly as impressive as the article title makes it out to be.