1. A security screening system comprising: a main housing; a contact pad provided on the main housing; a sample collection sheet positioned upon the contact pad, said sample sheet receiving a trace residue sample upon contact with a subject; a pressure sensor operatively linked to the contact pad, said sensor configured to determine a pressure applied to the contact pad by the subject during a sample collection process; a sample processing system provided in the main housing, said sample processing system analyzing the sample collection sheet to determine whether the trace residue sample contains a threat residue; and a spatial recognition system operatively connected to the sample processing system, said spatial recognition system configured to focus the sample processing system on particular portions of the sample collection sheet contacted by the subject.