"Silent witnesses", оr to the question using physical evidence, obtained with law violation
In order to provide strict compliance of established criminal proceeding order and to investigate crimes effectively physical evidences, like other kinds of evidence, must satisfy some requirements, admissibility as well. Nowadays, unfortunately, too often we meet the cases when important and material data, objects, obtained on the crime scene, and other evidence are declared as «obtained with law violation» and deleted from the list of evidences. Such cases lead to defendants' discharge.