The Latin phrase ex post facto means “from a thing done afterward.” In law, it refers to a criminal statute that retroactively punishes conduct that was legal at the time it was committed. The United States Constitution expressly prohibits such laws under:
A presumption of innocence means that any defendant in a criminal trial is assumed to be innocent until they have been proven guilty. As such, a prosecutor is required to prove beyond a reasonable doubt that the person committed the crime if that person is to be convicted. To do so, proof must be shown for every single element of a crime.
