Factors affecting the intelligibility of recorded speech: Considerations for forensic audio “best evidence”.

Abstract

Derived from a traditional common law rule of evidence, the “best evidence” standard as applied to recorded audio prescribes that an original recording, and not a duplicated or altered copy, will be presented in legal proceedings. The intent of this standard is to ensure that the integrity of the original evidence is preserved, such that a court is reasonably assured that it is being presented with the most complete and accurate record of the evidence. However, when considering forensic audio recordings of speech, which are frequently made in adverse acoustic environments, presentation of such recordings in their original form may not afford a court with the opportunity for a complete and accurate assessment of the evidence in question—namely, what words are being spoken on the recording? The current paper summarizes the technological and listener-based factors that should be considered when speech intelligibility is of prime importance in meeting the best evidence standard for presentation of forensic audio in court proceedings. Illustrative examples from recent court cases will be provided.