A HOMICIDE INVESTIGATION INVOLVES INTEGRATING INFORMATION FROM AT LEAST THREE SOURCES: THE MEDICAL EXAMINER'S REPORT; THE WORK DONE ON PHYSICAL EVIDENCE BY THE FORENSIC SECTION AND OTHER RESEARCH UNITS; AND THE INVESTIGATION DONE BY THE HOMICIDE DETECTIVE. MOST HOMICIDE DETECTIVES AGREE THAT THE CRITICAL PERIOD IN AN INVESTIGATON IS THE INITIAL RESPONSE TO THE SCENE AND THE HOURS IMMEDIATELY AFTERWARD. AN ESSENTIAL PART OF THE CRUCIAL FIRST HOURS IS THE UNIFORMED OFFICER WHO IS FIRST TO ARRIVE AT THE SCENE. THE OFFICER'S MOST IMPORTANT RESPONSIBILITY IS TO PRESERVE THE SCENE INTACT -- SECURING THE ROOM OR AREA IN WHICH THE CRIME TOOK PLACE, NOT TOUCHING POTENTIAL SOURCES OF FINGERPRINTS, NOT MOVING THE CORPSE, KEEPING PEOPLE AWAY FROM THE SCENE, KEEPING TRACK OF WITNESSES, BEGINNING THE SEARCH FOR EVIDENCE OUTSIDE THE ACTUAL CRIME SCENE, AND TAKING NOTE OF PERISHABLE EVIDENCE (E.G., ICE CUBES MELTING IN A DRINK, A WARM RADIO OR AUTOMOBILE). GUIDELINES FOR OFFICERS WHO ARE THE FIRST TO ARRIVE AT A HOMICIDE SCENE ARE PRESENTED, AS IS A BRIEF DESCRIPTION OF THE FORENSIC SCIENTIST'S RESPONSIBILITIES. PHOTOGRAPHS DEPICTING HOMICIDE INVESTIGATIONS ARE INCLUDED. (LKM)