Measuring the Photon Polarization in Radiative B --> K-pi-pi-gamma

We propose a way of measuring the photon polarization in radiative B decays into K resonance states decaying to K{pi}{pi}, which can test the Standard Model and probe new physics. The photon polarization is shown to be measured by the up-down asymmetry of the photon direction relative to the K{pi}{pi} decay plane in the K resonance rest frame. The integrated asymmetry in K{sub 1}(1400) {yields} K{pi}{pi}, calculated to be 0.25, is measurable at currently operating B factories.