Hi, Katherine...they used the equipment available in the police dept, which can enhance sound, delete all sound, sharpen the picture, slow-mo, voice prints/patterns, voice overlay, etc.  Basically the same thing you see in TV shows (Without A Trace, CSI).  It is as reliable as it can get until newer equipment is invented, so I accept the findings.  I know some viewers will still be skeptical and continue in this beliefs, but that's OK.  This wasn't to prove whose right or wrong, and I guess I should have put a message at the beginning of my post to alert viewers so if they didn't want to know, not to read further.