The rules associated with academic misconduct are built around an academic process used at many peer universities. While it draws on some aspects of court of law in processes and terminology, such as requiring evidence to find a student in violation of the Honor Code, it does not have the weight of law or the same requirements on proof.
The test for a student to be found responsible for academic misconduct is "preponderance of the evidence." This translates to a 51% certainty that the violation occurred based on the evidence presented.
This does not mean that the instructor or Honor Council must prove beyond a reasonable doubt that the student committed academic misconduct or explain every detail of how it was executed and why. Trying to counter the physical evidence (such as an assignment with your writing on it or submitted using your email or NetID) with theories of tampering by an unknown person having an unknown motivation will not provide adequate proof to overcome the "preponderance of the evidence" test.