Methods and apparatus for early detection and identification of a threat such as individuals carrying hidden explosive materials, land mines on roads, etc. are disclosed. One method comprises illuminating a target with radiation at a first polarization, collecting first radiation reflected from the target which has the same polarization as the first polarization, illuminating a target with radiation at a second polarization, and collecting second radiation reflected from the target which has the same polarization as the second polarization. A threat determination is then made based on the difference between the energy values of the first and second collected radiations. In other embodiments, the difference between energy values is used in conjunction with an evaluation of the returned energy in comparison with returned energy from other targets in order to additionally assess whether the primary target is a threat.