It has further been established that the question of admissibility of audible portions of tape recordings, when certain portions were inaudible, was properly addressed to the discretion of the-trial court. This evidence may be circumstantial or direct, real or testimonial, and need not conform to any particular mode. Therefore, according to the more liberal admission rulings, a tape recording may be admitted into evidence if a proper chain of custody is proven. Or, if the chain is not strong enough, the proponent of the tape may submit it to a qualified forensic expert for authentication. The Ninth Circuit said that the trial court, in the exercise of its discretion, must be satisfied that the recording is accurate, authentic and generally trustworthy.
Prosecutors often request investigation of deficiencies in the previously mentioned process.
Most often, however, a forensic expert is contacted when the tape is believed to have been altered or tampered with. Due to the nature of the allegations surrounding tampering issues, the examiner will requirements specific items from the party. Power source, including a portable generator or drycell batteries 2. Environment, such as telephone transmission line, restaurant, apartment, street, etc. Background noises, such as television, radio, unrelated conversations, computer games, etc. 5.