Explosive devices can be left in virtually any package in any place. There are people trained to respond to potential bomb threats, referred to as the bomb squad. The bomb squad will disarm, dispose of, or declare a bomb safe. In the case that the bomb detonated, these professionals will use clues left at the scene to “help identify the type of device used and gather all available physical evidence or witness testimony that could help lead to the bomber” (“A Simplified Guide”). Any part of the bomb the investigators find (circuit board, hair, etc.) could assist in leading back to the person that put the bomb together.
The two types of bombs used are explosive or incendiary, or can be a combination of both. Explosives use materials meant to explode, and incendiary are meant to cause a fire. The speed of an explosive determines its classification. Explosives that react faster than the speed of sound (dynamite, TNT, C-4, acetone peroxide) are strictly controlled so they are not as easy to obtain. Low explosives (gunpowder, fireworks) burn slower, and react at less than the speed of sound, so these are actually called deflagrations instead of detonations when they are set off.
Some common explosive devices are pipe bombs, improvised exploding devices (IEDs), and Molotov cocktails, which start fires upon impact. Any of these will leave evidence at a scene, which is then collected and examined. Evidence can also be collected from the bodies of victims or the suicide bomber responsible for the explosion. This evidence is carefully examined by trained teams to try to link the bomb back to the owner. In the case of terrorist bombs, the Terrorist Explosive Device Analytical Center (TEDAC), run by the FBI, is called in to investigate.
Explosives can cause major damage and result in injury or the loss of life. Any bomb threat should be taken seriously, and if a detonation cannot be prevented, professionals are capable of examining the evidence to bring the perpetrator to justice as quickly as possible.
Source: “A Simplified Guide to Explosives Analysis.” Forensic Science Simplified.” 2013. Web. 10 January 2016.