  Gravitational Compton scattering process with a massive fermion is studied in
the context of the linearized gravity. Gravitational gauge invariance and
graviton transversality cause the transition amplitude to be factorized into
that of scalar QED Compton scattering and that of fermion QED Compton
scattering with an overall kinematical factor. The factorization is shown
explicitly and its physical implications are discussed.
