THE PSE IS BASED ON THE OBSERVATION THAT THE HUMAN VOICE NORMALLY CONTAINES A LOW FREQUENCY, INAUDIBLE, INVOLUNTARY MUSCLE TREMOR, WHICH IS ABSENT WHEN THE SPEAKER IS UNDER PSYCHOLOGICAL STRESS. BECAUSE LYING CAUSES PSYCHOLOGICAL STRESS, THE TREMOR'S ABSENCE AS INDICATED BY THE PSE, POINTS TO THE SPEAKER'S GUILT. THE PSE IS MUCH SIMPLER THAN THE POLYGRAPH, WHICH REQUIRES CONSIDERABLE EQUIPMENT AND OFTEN PRODUCES STRESS IN THE PERSON BEING EVALUATED. USE OF THE PSE PERMITTED RILEY BROOKS, A MARYLAND RESIDENT SENTENCED TO LIFE IMPRISONMENT FOR MURDER, TO ESTABLISH HIS INNOCENCE. A STUDY OF 43 CRIME SUSPECTS IN MARYLAND SHOWED 100 PERCENT CORRELATION BETWEEN THE PSE RESULTS AND INDEPENDENT FINDINGS OF GUILT OR INNOCENCE. NUMEROUS OTHER ANECDOTES AND CASES ILLUSTRATE THE PSE'S POTENTIAL FOR PROTECTING PEOPLE FROM BEING FALSELY ACCUSED FOR CRIMES. PHOTOGRAPHS AND AN ILLUSTRATION OF A GRAPH PRODUCED BY A PSE STYLUS ARE INCLUDED. (CFW)