At which point does a hack become criminal? Probing defences? Breaching defences? Accessing your own, stolen data? Downloading it? Downloading everything else?

At which point does a hack become criminal? Probing defences? Breaching defences? Accessing your own, stolen data? Downloading it? Downloading everything else? If I see the guy who stole my car, nick the car keys from his pocket and drive off, is that theft? What if my car also has his wallet, and I drive off with that?