Watch transactions that people make and compare to what they do in real life. It is tedious work and takes time, but governments do similar things to investigates lots of crimes. If you murdered one person you would probably get away with it so long as you are not obvious about it (don't murder your wife - you become the obvious suspect and probably can't hide your trail), but most criminals commit several crimes and eventually all the different trail of evidence add up to an arrest. Likewise if you only have one crypto transaction you won't be found, but for crypto to be useful you need to use it and eventually that leaves enough of a real world trail to figure out who did what.