a tiny crack, and inside was a minute piece of what looked like foam. >> it was nothing short of a miracle that the tiny piece of foam had stuck in the prop when you consider the dynamic forces going on. >> trace evidence expert ron stanbro analyzed the material under a microscope. >> i did not have very much sample to work with, but it was more than enough for the analysis that we were required to do. >> the foam from the propeller looked very similar to the foam padding from the seat in harry uhl's boat. so, stanbro went a step further, using a process known as fourier transform infrared. >> it's shining an infrared light through that substance, and the molecules within that substance are stretching and vibrating, and then we're measuring the absorbance of that infrared light in that sample. >> this provided a chemical fingerprint of the polyurethane in both samples.