[Udo]

> If I've actually committed a crime

The article (and other such presentations on the subject) indicate very clearly that innocence is not a factor. It doesn't seem to matter if you've committed a crime or not - and whether your assessment your own innocence itself actually holds true or not is yet another uncertain factor.

> if someone's committed a crime against me

Then your lawyer will facilitate all the necessary measures, and he/she'll do it better and more efficiently than you ever could.

> What determines when I should be talking to the cops and when I shouldn't?

Beyond basic cooperation at, say, a traffic stop or during an emergency, most experts seem to agree that you should never, under any circumstances talk directly to any law enforcement personnel.