I am not bashing you, Hangn, and I've done my share of what I would consider to be inappropriate snooping, myself. Whether it SHOULD be OK or not is a matter of debate. I just don't want people to think it's perfectly OK from a legal standpoint.
And legality DOES matter. As much as a person might want to record some of the awful/crazy things the alcoholic says, there are actual criminal penalties for secretly recording someone in a significant number of jurisdictions. I don't want to see anyone jammed up for trying to protect themselves, that's all. It's always best if you think you have the right to do something along those lines to get legal advice first.