As others have said....

It's not your place to get into who's right and who's wrong. That's why you have a (hopefully) functional legal system over there.

If you actually saw the tape, but don't remember what you saw on it, say that.

If you don't remember ever seeing the tape, say that too.

If your boss threatens to fire you if you don't testify as per his advice, tell him you're calling the local prosecutor and having him charged with conspiracy to commit perjury and that you're starting a civil suit for wrongful termination/harassment.

That should settle him down pretty quickly.

It's not okay to steal to make up for being screwed over by your company either, btw. I understand your (and your former co-worker's) mindset on this, but that's just vjigilantism. He should have reported it to the local labor bureau. Even in the US, he would have gotten some satisfaction.... in a socialist paradise like Norway, he may have wound up with your boss as a manservant for life.