  We consider the quantum scattering from a random potential of strength
$\lambda^{1/2}$ and with a support on the scale of the mean free path, which is
of order $\lambda^{-1}$. On the basis of maximally crossed diagrams we provide
a concise formula for the backscattering rate in terms of the Green's function
for the kinetic Boltzmann equation. We briefly discuss the extension to wave
scattering.
