Application of the Electrical Network Frequency (ENF) Criterion. A case of a digital recording

One of the new methods of investigating the authenticity of evidential digital audio recordings uses the Electrical Network Frequency (ENF) Criterion. It is based on analysing the signal corresponding to the fundamental frequency of the current in the electrical network, which is present in a recording and comparing it with appropriate, reliable reference. Studies carried out at the Institute of Forensic Research in Cracow were aimed at validating this method, that is, assessing its usefulness in forensic examinations of evidential digital recordings in Poland. These studies enabled us to develop and implement a procedure for using the ENF Criterion method to assess the integrity of digital recordings and to establish when these recordings were made.