Earlier this week, it was reported that Spears's ex-partner Jason Alexander claimed to have audio of the singer retelling the circumstances of the assault.
TMZ reports that Tom Owen of OWL Investigations, who is also chairman of the Audio Engineering Society Standards Committee of Forensic Audio, told the website that the tape was "doctored" to the extent that it is not possible to carry out voice-recognition tests.
Owen said that the tape has been "stepped on at least three times", which has changed elements such as the voice's natural timbre and tonal qualities.
He added that because of Spears's naturally "vanilla" voice, it would not be hard to manipulate audio to make someone sound like her.
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