I wonder how the “source” determined that the sound of a saw was coming from the recording. And why would there be a recording?
IIRC, there was some story about the execution being recorded from or by a cell phone, but I think it’s more likely the Turks had simply “bugged” the Embassy.
More straightforward is the analysis of the audio - if the sounds are fairly clear, use of a saw might be obvious. If not so clear, a little audio forensics might be in order. The equivalent of any State Police lab in the US, or whoever they might contract out to, could likely handle it.