Using a simple exact analysis of the one-photon optical transition amplitudes for the emission of correlated electron pairs from randomly oriented targets it is shown that information on the phase differences of these amplitudes can be obtained by the variation of the helicity of the absorbed photon. Experiments performed with different polarization of the photon can be related to each other by analytical formulae that should be used as a consistency check. The usefulness of this approach is demonstrated by analysing recent experimental and theoretical data.