I watch shows like The First 48 and others and I notice they always have the phrase "presumed innocent until proven guilty". If they are truly presumed innocent, it seems to me the phrase should be "presumed innocent UNLESS proven guilty". I was wondering where this phrase originated. Is it part of the law or just something the TV shows came up with as their disclaimer?
As to its original origins, I can only really speculate - Wikipedia, with a citation, credits the phrase to an English lawyer Sir William Garrow, who lived during the mid 1700's.
That said, the phrase is expressly adopted by many jurisdictions now, including your home state, Illinois. Section 3-1 of the Illinois Criminal Code states that "Every person is presumed innocent until proved guilty. No person shall be convicted of any offense unless his guilt thereof is proved beyond a reasonable doubt."
So, this is probably the one rule of law the TV shows may actually be representing correctly.