The common starting point of the phase-consistent γ-ray angular distribution theory of Rose and Brink is generalised to cover the case of photon emission from mixed ensembles. The result may be looked upon as a phase-consistent generalisation of the well-known “golden rule” which now may be applied to physical ensembles that need not necessarily be in pure states. The result is obtained by straightforward application of time-development techniques in combination with density matrix formalism, using a quantum-electrodynamic interaction and standard first-order perturbation theory.