In which amendment is it specified that you are innocent until proven guilty?

The idea of being innocent until proven guilty does not appear in any of the Constitutional amendments, but is, in fact, a part of common law. It is not a right granted by the Constitution.

"Innocent until proven guilty" means only that a defendant has a presumption of innocence, which is why the outcome of a trial is "not guilty" instead of "innocent." Common laws are laws adopted from English jurisprudence. They have been part of the legal system for so long that they have been universally accepted as U.S. law. The Constitution does, however, provide provisions allowing for the right to remain silent if detained, as well as the right to a trial by jury.