System and method for XRD-based threat detection. An object is scanned with a first threat detection system. One or more alarm objects are identified. Data about the one or more alarm objects is passed from the first threat detection system to a second threat detection system and is used to move and/or to rotate the object in a predetermined ray path that decreases attenuation of scattered x-ray radiation. Also disclosed is a secondary collimator for XRD-based false alarm resolution in computed tomography {“CT”) threat detection systems. The secondary collimator comprises one or more slit apertures configured to provide a multi-angle capability that extends a range of momenta for which XRD intensities are measured for a predetermined range of photon intensities.