MODERN PSYCHOLOGY HAS DISCARDED THE CONCEPT OF THE IDEAL OBSERVER AS A PURELY RECEPTIVE AND PASSIVE MECHANISM, WHO RESPONDS COOPERATIVELY TO LIGHTS AND TONES WITH UNBIASED EYES AND EARS, MUCH LIKE A MACHINE. UNLIKE MACHINES, HUMAN OBSERVERS PROCESS THE INPUT THEY RECEIVE AND REACH A CONCLUSION BASED ON PRIOR EXPERIENCE, FAMILIARITY, BIAS, EXPECTANCY, DESIRE TO APPEAR CERTAIN, ETC. THUS, EYEWITNESS TESTIMONY IS UNRELIABLE EVEN UNDER IDEAL CIRCUMSTANCES. A VICTIM OR WITNESS OF A CRIME HAS BEEN SHOWN BY RESEARCHERS TO BE LESS CAPABLE OF REMEMBERING DETAILS, LESS ACCURATE IN READING DIALS (TIME DETERMINATION), AND LESS ACCURATE IN DETECTING SIGNALS BECAUSE THEY HAVE BEEN PAYING MORE ATTENTION TO THEIR OWN SAFETY THAN TO NONESSENTIAL ELEMENTS IN THE ENVIRONMENT. SUCH FACTORS AS PRIOR CONDITIONING AND EXPERIENCE, AS WELL AS PERSONAL BIASES AND STEREOTYPES COLOR AND ALTER THEIR REPORTS. FOR EXAMPLE, AN EXPERIMENT CONDUCTED ON A COLLEGE CAMPUS, IN WHICH A DISTRAUGHT STUDENT ATTACKED A PROFESSOR IN FRONT OF 141 WITNESSES, WAS RECORDED ON VIDEOTAPE. THE WITNESSES WERE ASKED TO WRITE SWORN STATEMENTS DESCRIBING THE INCIDENT, THE SUSPECT, AND THE CLOTHES WORN. THE STATEMENTS WERE THEN COMPARED WITH THE ACTUAL RECORDED EVENT. THE A WHOLE AND OF THE SUSPECT IN PARTICULAR, WHOM THE WITNESSES WERE ASKED TO IDENTIFY FROM STILLS OF THE INCIDENT 7 WEEKS AFTER THE FACT. ONLY 40 PERCENT OF THE WITNESSES CORRECTLY IDENTIFIED THE ASSAILANT; 25 PERCENT OF THE WITNESSES IDENTIFIED THE WRONG MAN AS THE ASSAILANT. ALL RELEVANT RESEARCH POINTS TO THE UNRELIABILITY OF EYEWITNESS TESTIMONY. A LIST OF 21 REFERENCES IS INCLUDED. (LGR)