what i want to know is...how exactly did they determine the "illegal" mp3s?

what if he bought some, friends gave him some (of their own stuff for argument's sake), and then he downloaded some? most people i know actually do use a combination of these, so how do the authorities make that determination.

i would think that would be pretty importanat if they're gonna fine you 200 euros per mp3 to know exactly which ones are he naughty ones, dontcha think?