It is a legal term but is not meant to be carried out in public, or even in the legal system, to an absurd degree, as if that were the case, we would never arrest and lock up anyone until they were found guilty by a court of law IMO. Moreover, in my view, sometimes guilty people walk free. That doesn't mean they are innocent of the crime by strict definition in our society - just that they were not found guilty in a court of law and need to be afforded what legal rights the rest of us have. We don't have to think of them as innocent. They can even confess to a crime after the fact, since we have double jeopardy laws. There is innocent and guilty in the legal sense, and innocent and guilty as words we use to describe whether someone did something or not. I am probably making a mess of the legal points, above, but hopefully I am making some rational point here.