I don't necessarily believe a Constitutional amendment is necessary, since this would be a law limiting government reach, not extending it.
In all likelihood, the amendments text would look something like:
> Section 1: The fourth article of amendment to the Constitution of the United States is hereby extended to include information or detail held, owned, or otherwise under the custody of those other than the accused.
> Section 2: The Congress shall have power to enforce this article by appropriate legislation.
Which then necessitates some accompanying legislation to further clarify. But I'm pretty confident we can get there through legislation alone.
In all likelihood, the amendments text would look something like:
> Section 1: The fourth article of amendment to the Constitution of the United States is hereby extended to include information or detail held, owned, or otherwise under the custody of those other than the accused.
> Section 2: The Congress shall have power to enforce this article by appropriate legislation.
Which then necessitates some accompanying legislation to further clarify. But I'm pretty confident we can get there through legislation alone.