  In a recent experiment [McGehee et al., Phys. Rev. Lett. 111, 145303 (2013)],
the expansion of non-interacting ultracold fermions was studied in a random
speckle potential, and the observed density profiles were interpreted based on
3D Anderson localization. The purpose of this note is to demonstrate that slow
diffusion of particles with a broad energy distribution and an energy-dependent
diffusion coefficient leads to density profiles that agree with the measured
data, but not with the behavior expected for 3D Anderson localization.
