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Arson Investigation (The following topic was presented at the April 8, 1995 SCAFO meeting)
Speakers MICHAEL SMOLLEN Arson is the burning of property with the intent to do harm and/or burning with the intent to defraud. If you burn your own property but do not claim anything, it is not arson, but you will probably be violating other state or city laws and ordinances. Arson is now an epidemic in this country. In hard economic times, the number of arson fires usually increases, as do claims for business losses. What do you think would be the most common thing people would use to set fires? Gasoline is number one except for professional arsonists. They walk into buildings with nothing more than a match. They do not want anyone to know they set the fire. They want it to look like an accident. Normally at an arson scene, the first step in determining the cause of a fire is to locate the area or place where the fire first began. We will start from the outside and work our way from the unburned to the burned. What we are looking for is the room of origin and then the point of origin. So we work backward and follow the path of the fire in reverse order. The point of origin and the cause of the fire are usually related. The cause of the fire can usually be located near or at the point of origin. The exceptions to this rule would be incendiary fires caused by flammable accelerants or fires resulting from accidental flammable liquid spills. Fires usually burn for longer periods near the point of origin. This is due to sufficient oxygen available during the early stages of fire. Fires then will grow upward and outward from the point of origin. Evidence of incendiarism (deliberate setting of a fire or fires by a human being) is often recovered near the point of origin such as accelerant residue, combustibles, devices and prior preparations for burning. Evidence of the fire spread or direction of fire travel may be noted after locating the point of origin, such as natural versus unnatural spread and unnatural burning or intensity of the fire. In attempting to locate the origin of a fire, first examine areas of little or no damage and work toward an area of severe fire damage or lightly charred areas to heavily charred areas. Second, check the ceiling for damage. The area above the point of origin is usually exposed to heat and flame for longer periods and may result in holes in the ceiling. Confirm that damage is not due to “overhaul” operations. (Overhaul is the procedure of inspecting the premises after extinguishment to insure that the fire is completely extinguished and will not rekindle later on). When investigating a building fire, look for low burn areas. Fire wants to go up so if it goes down, usually some type of flammable liquid is causing it to go down. They usually will not burn unless something is holding the fire down low to the ground. Most accidental structural fires produce very little floor charring. Temperatures at floor level are usually below ignition temperatures for most common combustible materials. “V” patterns may help identify the point of origin. Normal growth of fire is upward and outward and this burning frequently produces “V” burn (char) patterns above the point of origin. The “V” will usually point toward the origin of the fire. In large fires, the “V” pattern may be identified only when viewed from a distant location or from above. Structural members will usually suffer more damage on the sides, surfaces, edges and corners first exposed to the heat and/or flame. Flammable liquids may run through the flooring, burning under the floor (investigator must show that charring did not come from below.) On tile floors they can produce unusual burn patterns such as “ghost marks” between and under the tiles. Flammable liquids may also be carried behind base boards and moldings. They may also produce unusual burning of contents--—burning the bottom surfaces of doors is usually an indicator of flammable liquids at floor level. The burning of the floor surface along the edge at contact with walls may be due to the presence of flammable accelerants. The corners and wall to floor edges are usually dead air spaces that suffer little, if any, fire damage unless flammable accelerants are present. The charring of the underside of most furniture or appliances is unnatural, unless flammable liquids were used. Light bulbs can also be used to locate the point of origin. Light bulbs will usually begin to swell or distort when exposed to 900oF for approximately 10 minutes. The side of the bulb nearest the point of origin usually reaches distortion condition first. One indication would be a swelling on the side toward the point of origin or it may blowout toward the point of origin. Also, when investigating these fires, use your nose, as flammable liquid odors can usually be detected during and after the fire. Residue on objects should be collected as soon as possible and be sent in for analysis. To collect evidence, the best thing is still a clean paint can. The discovery of flammable liquid containers can provide a comparison sample for laboratory analysis, as well as fingerprint identification. There is a problem looming with new paint cans that are coated on the inside with a grey substance. Presently, tests are being conducted to see if they contaminate evidence placed in these new cans. “Trailers” may be used to start the fires. “Trailers” are combustible materials such as rolled rags, blankets, newspapers or flammable liquid used to spread the fire from one point or area to other points or areas, often used in conjunction with an incendiary device. You also want to look for holes in walls, fire doors propped open or drapes closed in a single family dwelling. Look for things that are suspicious or out of place. Also look for things that are not in their normal locations. Is what is supposed to be here, here? Most people who set arson fires to their own homes will remove items that are irreplaceable--— photo albums, jewelry, clothes, etc. Check to see if personal items were removed or destroyed in the fire. Photography at the fire scene can be an extremely valuable tool to the arson investigator. If you respond while the fire is still burning, take some long shots (photographs) and note the time and location of the shots. Then move in closer and take some medium length shots and then some close--up shots of the fire. Also, try to get photographs from different sides of the fire. The color of the flame can sometimes tell you what temperature the fire is burning at and give an indication of what is burning, so take a lot of pictures of flames. Also, the color of the smoke can tell you at what phase the fire is in, whether it is black, grey, brown, or white. Take pictures of the crowds—arsonists love to see their work and have been identified from photographs of crowds at fire scenes.
This article was originally published in “THE PRINT” |