Be sure to include electrical outlets in the area(s) around the most fire damage (possibly the origin of the fire), and the breaker box and switches. Make note of any "tripped" switches, wiring and/or connections (electrical, phone, cable, etc.) leading to the building, as well as gas meters and any other external devices connected to the building (A/C or HVAC unit). Photograph and document any electrical items (all angles) and the outlets they are plugged into within the burned area or areas, if the origin cannot be initially
determined.
Prepare to identify, collect, and preserve evidence from the fire scene as you would for any other incident or crime. However, there are some factors to consider when collecting evidence from a fire, since certain items may need to be evaluated by laboratory personnel. Make sure to send those items to the laboratory immediately following the incident.
Items suspected of having an ignitable liquid accelerant on or in it will need to be preserved in a container that traps chemicals and vapors, including wet or dry samples. Evidence "paint cans" will work well. If the item or items will not fit into cans, seal them in a large static free "k-pack" bag, but make sure to read about the specific product's instructions and limitations.
There are also additional considerations on how evidence "paint cans" can be stored prior to their use. If cans are in the trunk of a vehicle, make sure they are clean and unused, and tightly sealed in k-pack bags.
In court, the defense will probably not be able to challenge the lab results. However, they may challenge or try to create doubt about the state of the cans before evidence was collected. If the cans are stored in the trunk of a car, the defense may attempt to persuade the jury that the cans were exposed to the vehicle's
exhaust.