Audio evidence includes confidential informant recordings, recordings of confession by officials, telephone intercept or wiretap, voice mail, and 911 calls. The goal of the forensic expert is to process the recordings for forensic enhancement and or forensic authentication and analysis.
One step in the forensic authentication process of video recordings is to be sure a chain of custody has been established. Also, is the recording used as evidence an original or a copy? The audio portion of a video recording is also examined forensically when performing forensic video authentication.
This was important back when analog recordings were primarily used as evidence. This is because the audio portion of a video recording holds many clues for the forensic examiner. It is especially important today with digital recordings being the primary format for audio evidence. Once the digital recording has been burned to a CD, it is no longer considered an original. Especially if anybody objects to its authenticity. It is considered a digital duplicate as long as all parties in the litigation agree to its contents and what it pro-ports to show. It is much more appropriate to use the original recording because it can be forensically authenticated when it is in its original environment.
There is no reason that an original digital audio recording cannot be preserved in the equipment that created it.
Digital audio recordings take up very little space and can easily remain stored on the equipment that created it. It is not okay to erase or delete the original so the recording equipment has more storage space. In the case of a digital pocket recorder deleting content to make room may be a logical thought process until somebody objects to its authenticity.
In some cases, a deleted audio recording could be considered spoliation of evidence if a forensic expert can not effectively authenticate the audio evidence. A CD copy is technically not an original because once the audio recording is removed from its native environment. Often times, this alteration can go undetected even by an experienced audio forensic expert. This is why preserving the original file of the audio evidence is extremely important.
Whether you are law enforcement presenting a confidential informant or confession audio recording, a private individual presenting a voice mail or concealed audio recording, always preserve the original recording so there is no doubt of the authenticity and integrity of the audio evidence. Consult an experienced audio forensic expert to assist you in authenticating the audio evidence for a fair and accurate representation of the facts as they occurred in their original environment.