Here is an interesting case from FederalEvidence blog on how the 8th Circuit deals with the scratchy issue of a poor audio recording.
Factors For Admitting “Partially Inaudible” Recordings
Eighth Circuit rules that partially inaudible recordings with a confidential informant may be admitted when the trial court finds that they “provide [the] jury with the ‘gist’ of the conversations” so that any inaudible portions do not “render” the tapes untrustworthy as a whole, in United States v. Trogdon, __ F.3d __ (8th Cir. Aug 6, 2009) (No. 08-2858).
Here is CAAF on the subject.
In our 1992 decision in United States v. Banks, we provided guidance to trial judges dealing with audiovisual evidence. We encouraged the use of transcripts “as an aid in presenting evidence with audio dialogue” and suggested that “the military judge indicate if he or she has viewed or listened to the proffered evidence prior to ruling on its admissibility.” We also noted that when such a tape’s “audio is poor, a transcript could assist both the trier of fact and appellate courts.” The admission of the transcript in this case was consistent with Jewson, Turner, and Banks.
United States v. Craig, 60 M.J. 156, 160 (C.A.A.F. 2004).
We generally agree with the Ohio Supreme Court that, once a proper foundation is laid, “recorded tapes of actual events, such as street drug sales, should be admissible despite audibility problems, background noises, or the lack of crystal clear conversations, since they directly portray what happened.” However, this rule is subject to the caveat that a recording is not admissible if “the unintelligible portions are so substantial as to render the recording as a whole untrustworthy.” If only a part of the tape is inaudible, the military judge must determine whether those portions are so substantial as to render the entire tape untrustworthy and thus inadmissible. The military judge should clearly state on the record which portions of an audiotape are inaudible.
United States v. Craig, 60 M.J. 156, 160 (C.A.A.F. 2004).