The four principles of digital evidence. Electronic evidence is fragile and if not handled correctly it may be lost or altered. The UK Association of Chief Police Officers “ACPO Good Practice Guide for Digital Evidence” was first introduced in 1999. The guide can be summarized in the four key principles shown below. The principles have been thoroughly tested in court many times. If you need to handle electronic data that may be used as evidence in court, before you do anything ask yourself will your actions comply with the four principles? if they don’t then your evidence may not be allowed to be admitted as evidence in court.