Is A Person Really Innocent Until Proven Guilty??

This is always a comment brought up when talking about a person being taken to court. Its is known that a person is always innocent until proven guilty but when someone is brought to court a jury always has some type of agenda or bias towards someone. It may be cause they have heard things about this person or it may be that they produce a bias about them based on their appearance. So with all the bias in the world, is anyone really innocent in the eyes of others?? Therefor, it must take a lot to be proven guilty..