This student seems both cocky and clueless in equal measures. Fingerprints are not one of a kind, it's a very useful method as they rarely repeat exactly but they do so are not used in isolation but rather as part of a case.

I'm not sure why he's going on about different fingers on the same person being similar but not the same, that's known and kind of irrelevant, you can't convict someone with "your fingerprints are kind of similar to this one" without further convincing evidence.