  We investigate the effects of spin-flip scattering on the Hall transport and
spectral properties of gapped Dirac fermions. We find that in the weak
scattering regime, the Berry curvature distribution is dramatically compressed
in the electronic energy spectrum, becoming singular at band edges. As a result
the Hall conductivity has a sudden jump (or drop) of $e^2/2h$ when the Fermi
energy sweeps across the band edges, and otherwise is a constant quantized in
units of $e^2/2h$. In parallel, spectral properties such as the density of
states and spin polarization are also greatly enhanced at band edges. Possible
experimental methods to detect these effects are discussed.
