Case files of investigations – akta postępowań przygotowawczych (case files of prosecution proceedings) conducted by the investigative units of the security police were filed in the archive usually in the repository under reference number ‘III’. The files were of a particular character – i.e. they were the documentation of investigations run by the security service to produce material for the state prosecution service. The investigative unit was not the operational unit that ran surveillance, although it was provided with some documents and information gathered clandestinely. The investigative files did not always mirror the documentation handed to the prosecution service (certainly the secret sources of the security police were not disclosed), and could contain information or documents that were not passed on. The usual content of the investigative files are : protocols of interrogations led by security police officers, documentation concerning arrests, searches, and objects seized, detention of suspects, etc., plans and notes concerning an investigation, as well as blueprints of indictments, and copies of sentences.