1. (Discussion and Textbook Assignment - Searching the Fire Scene)
Tuesday February 7, 2017
(Discussion and Textbook Assignment - Searching the Fire Scene)

2. Point of origin of the fire
The Daily CSI
Tuesday, 2/6/18
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What do fire investigators look for first once they begin to search the scene?
Point of origin of the fire
fuel B A C

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5. Searching the Fire Scene

6. Searching the Fire Scene
The CSIs begin searching the fire scene as soon as the fire is extinguished.
Most arsons are started with petroleum-based accelerants such as gasoline or kerosene.
The presence of containers capable of holding an accelerant arose suspicions of arson.
Another indication of possible arson is discovery of an ignition device (candle, time-delay device, etc.)
A common sign of arson may be an irregularly-shaped pattern on the floor or ground.
Investigators also look for signs of breaking and entering and theft.
Eyewitnesses are interviewed.

7. Timeliness of Investigation
Time works against the arson investigator.
Accelerant residues can evaporate within a few days or even hours. Accelerants in soil can be quickly degraded by bacterial action.
For safety and health reasons, cleanup and salvage operations must begin as soon as possible.
The need to begin an immediate investigation of the circumstances takes precedence over the requirement to obtain a search warrant to enter and search the premises.

8. Locating the Fire’s Origin
A search of the fire scene must focus on finding the fire’s origin, which will prove productive in finding an accelerant or ignition device.
The CSI must uncover signs of arson such as evidence of separate and unconnected fires or the use of “streamers” to spread the fire from one area to another.
For example, the arsonist may have spread a trail of gasoline or paper to cause the fire to move rapidly from one room to another.
Normally, a fire tends to move upward, and thus the probable origin is most likely closest to the lowest point that shows the most intense characteristics of burning.

9. Locating the Fire’s Origin
Sometimes as the fire burns upward, a v- shaped pattern forms against a vertical wall.
Because flammable liquids always flow to the lowest point, more severe burning on the floor than on the ceiling may indicate the presence of an accelerant.
If a flammable liquid was used, charring is expected to be more intense on the bottom of furniture, shelves, and other items rather than the top.

10. Locating the Fire’s Origin
Factors that contribute to the deviation of a fire from normal behavior:
Prevailing drafts and winds
Secondary fires due to collapsing floors and roofs
The physical arrangement of the burning structure
Stairways and elevator shafts
Holes in the floor, walls, or roof
The effects of the firefighter in suppressing the fire
All of these must be considered by the fire investigator before determining conclusive findings.

11. Locating the Fire’s Origin
Once located, the point of origin should be protected to permit careful investigation - nothing should be touched or moved before notes, sketches, and photos are taken.
An examination must also be made for possible accidental causes, as well as for evidence of arson.

12. Searching for Accelerants
Only under the most ideal conditions will combustible liquids be entirely consumed during a fire.
A portion of it will seep into a porous surface, such as cracks in the floor, upholstery, plaster, wallboard, or carpet.
Enough of the liquid may remain unchanged to permit its detection in the crime lab.
Fortunately, water used to put out fires does not interfere with lab methods used to detect and characterize flammable liquid residues.

13. Textbook Assignment – Searching the Fire Scene
Please get a Forensics textbook and a blank sheet of paper.
The title of your paper should be “Searching the Fire Scene.” Be sure to put your name and period on the paper!
Read and study pages 540 to STOP when you reach the heading titled “Collection and Preservation of Arson Evidence.” Take notes!
Write and answer the two questions below.
Why is it important that the arson investigator begin examining a fire scene for signs of arson as soon as the fire has been extinguished?
Where will an investigator usually locate the probable point of origin of a fire? What factors can cause a fire to deviate from normal behavior?