I know nothing about Polish law. However, I would point out that even if you are not criminally responsible for illegal actions done using Tor from your computer, that doesn't protect you from police investigation. Your life can be ruined even if your are, and are found by the court to be, innocent. Just imagine your name and face splashed across the newspapers with a story about you being charged with downloading/uploading child porn.
You would also need to make sure that your computer was squeaky-clean, since having arrested someone, law enforcement often gets a "we'll get him for something mentality", so if they find for example pirate material they might charge you with that even though it's unrelated to what they came for.
Last edited by cantab; 07-23-2010 at 08:55 AM.