The proton conduction mechanism of well-characterized SnP2O 7 and Sn1-xInxP2O7 materials was investigated using AC impedance spectroscopy and inelastic neutron scattering. Samples with minimal amounts of excess polyphosphate do not possess appreciable conductivity at room temperature. Indium doping appears to increase the high temperature proton conductivity of the materials. Inelastic neutron scattering data indicates that no appreciable changes in proton concentration occur between hydrated and dehydrated samples of SnP2O7 while changes in proton vibrational mode amplitudes occur with indium doping, or upon hydration, of samples that contain excess phosphate.