As people have more and more electrical devices in their home, it is often of great importance to determine whether these devices were the cause of a particular fire. The difficulty comes in that a short-circuited electrical wire that caused a fire will be damaged by that fire, as will any other wire that flames reach.
If a fire investigator suspects that a particular wire failed to cause a fire, there is an analytical approach they can take to determine if this is what happened. By analysing the crystal structure of the copper in that wire, measuring grain morphologies with EBSD, information on the aspect ratio of the grains can be used to indicate whether a particular wire caused the fire or was simply damaged by it.
This technique is based upon an understanding of the recrystallisation of copper with heat. Different heating and cooling events produce different grain textures in the copper. Essentially, if the aspect ratio falls within one range then that is indicative of the device having been subjected to the particularly high currents characteristic of a short circuit. If the aspect ratio falls within another range then that is indicative of the wire having been damaged by the fire.