This topic will describe arson and explosives investigations. In this chapter you will learn: Discuss the steps in the preliminary investigation of arson, be familiar with various types of burn indicators, describe ignition devices that may be used in arson, assess several common motivations of arsonists for setting fires, explain the scientific methods used in arson investigation, list several groups of people whom an arson investigator should interview,. | EIGHTEEN Arson and Explosives Investigations LEARNING OBJECTIVES Discuss the steps in the preliminary investigation of arson Be familiar with various types of burn indicators Describe ignition devices that may be used in arson Assess several common motivations of arsonists for setting fires Explain the scientific methods used in arson investigation List several groups of people whom an arson investigator should interview List questions that investigators should ask in interviews and interrogations Explain the two types of explosions Outline the procedures for handling and investigating bomb threats 18-1 PRELIMINARY INVESTIGATION One effective way to determine fire causes is to determine the point of origin The investigator should check for the level of origin by examining: the bottoms of shelves, ledges, moldings furniture and all sides of the legs, arms, and framework of reconstructed furniture The floor and lower areas of the room produce the most clues to the cause for the fire, because they are living area 18-2 WHERE AND HOW DID THE FIRE START? Two Factors Needed to Cause Fire During the investigation, it should be borne in mind that a fire always has two causes: a source of heat and material ignited Accidental Fires Once the point of origin has been discovered the next step is to determine how the fire started Even though arson may be suspected, the investigator must first investigate and rule out all possible accidental or natural causes 18-4 COMMON CAUSES FOR ACCIDENTAL OR NATURAL FIRES The electric system Electrical appliance and equipment Gas Heating units Sunlight Matches Smoking 18-4 SPONTANEOUS HEATING An increase in temperature that results from a natural process; caused by chemical action, fermentation, or exidation 18-5 SPONTANEOUS IGNITION The catching afire of materials subjected to spontaneous heating; usually requires several hours to several months of oxidation or fermentation 18-6 BURN INDICATORS Burn indicators are the effects of heat or . | EIGHTEEN Arson and Explosives Investigations LEARNING OBJECTIVES Discuss the steps in the preliminary investigation of arson Be familiar with various types of burn indicators Describe ignition devices that may be used in arson Assess several common motivations of arsonists for setting fires Explain the scientific methods used in arson investigation List several groups of people whom an arson investigator should interview List questions that investigators should ask in interviews and interrogations Explain the two types of explosions Outline the procedures for handling and investigating bomb threats 18-1 PRELIMINARY INVESTIGATION One effective way to determine fire causes is to determine the point of origin The investigator should check for the level of origin by examining: the bottoms of shelves, ledges, moldings furniture and all sides of the legs, arms, and framework of reconstructed furniture The floor and lower areas of the room produce the most clues to the cause for the fire, .
