was it really possible for leslie's body to float from where he said she fell to where she was found 150 feet and three waterfalls downstream? >> when we brought in the really top-notch water flow experts, we had to go back and try to duplicate the water flow as it was on the evening of the event. >> reporter: in august. 2009, 15 months after leslie died, investigators headed up to cottonwood creek to conduct some tests. they dressed a woman around leslie's size in similar clothing to what she wore the day she died. and positioned the female stand-in on the rock ledge, where fred said leslie landed before sliding into the water. >> the forensic people tried to float her from that location, where he alleged that she fell. the water did barely -- barely touched her body. >> reporter: so investigators put her in the water to see what would happen. >> she was then moved into the very center of that stream and it wouldn't budge her.