Local descent to quasi-split even general spin groups

Let n > 1 and let r be an irreducible unitary supercuspidal representation of GL(2n) over a local non-archimedean field. Assuming the twisted symmetric square L-function of r has a pole at s = 0, we construct the local descent of r to the corresponding quasi-split even general spin group GSpin(2n). We prove this local descent is generic, unitary, supercuspidal and multiplicity free. Its irreducible quotients are functorially related to r, in the analytic sense of a pole of a Rankin-Selberg type gamma-function.