No one can be considered guilty until their guilt has been established by a final court decision.
This is often referred to, and almost always incorrectly. So it is not that everyone is considered innocent until proven guilty, but that they cannot be considered guilty. This is a very small but very important difference in wording.
Of course, criminal liability can only be established if it has been proven beyond reasonable doubt. This is one of the most important legal principles, and it is probably the one that is most frequently violated worldwide.