  Interference effects form a fundamental pillar of quantum mechanics. In this
paper, we examine the interference in spin-orbit coupled transverse magnetic
focusing, where a weak magnetic field is used to focus charge carries over
mesoscopic scales. We determine a semi-classical form for the Green's function
in a weak magnetic field, for the case of both spin-less and spin-orbit coupled
charge carriers. The obtained forms for the Greens' function are independent of
particle dispersion and are thus applicable to a wide variety of systems.
