To avoid any contamination the team must make sure none of the evidence gets contaminated. To ensure this, all members of the team must use clean protective gear and equipment for each scene. Control samples are always needed in order to include or exclude evidence being tested. Each piece of evidence should be packaged and stored ready for transport and each piece of evidence should be separately packaged. These precautions are very important to have a successful crime scene investigation (A Guide for Investigating Bomb and Explosion Scenes: Evaluating the Scene, 2001).
To decrease the risk of contamination the scene must be investigated as soon as possible. Fire accelerants and explosive powders can evaporate within hours or days of the explosion. When collecting the evidence, every piece of evidence must be labeled, and sealed. Each piece of evidence must have a number, description, the location where it was found, the investigators name, and each marking identified must be logged. Each piece of evidence, components and fragments, including those recovered from victims must be collected and documented.
The materials that used to construct and transport the explosive device must be examined, along with residue which can be collected by swab techniques. Any other pieces of evidence such as hair, blood, fibers, or weapons also should be collected. Each piece of evidence must be photographed before being moved (A Guide for Investigating Bomb and Explosion Scenes: Evaluating the Scene, 2001). To determine what kind of bomb was used at the scene it is important to look for certain factors.
Before starting the investigation, the investigators must first determine if the explosion as an accident or if it was done intentionally. When analyzing the crime scene it is important to look for the source of the explosion, and look for igniting mechanism that may have been left behind and reconstruct how the explosion happened (A Guide for Investigating Bomb and Explosion Scenes: Evaluating the Scene, 2001). Some bombs can leave evidence behind that contains millions of different pieces depending on the type of bomb.
Materials used to make the bomb may be specific or follow a certain pattern of other explosions. Bomb fragments, residue from the explosive, bits of electronics, and sometimes even the bombers’ own fingerprints and DNA can all be found at the crime scene, and plays a significant role in linking the bomb to the bomber. There are a few ways to determine the type of bomb. If blasting caps are present it is easier to identify what kind of bomb was used. Forensic scientists use a portable ion mobility spectrometer test to test around the blast for trace of the explosive chemicals.
Some tests can determine the specific type of explosive by the chemicals in the air, which is then shown on digital readout. A color test can also be used, when the bomb residue mixes with substances that change color in response to specific explosives. These tests are considered accurate and can be confirmed at the lab with procedures like chromatography and mass spectrometry (A Guide for Investigating Bomb and Explosion Scenes: Evaluating the Scene, 2001). In order to fully collect all the evidence from the explosion, all pieces of evidence throughout the crime scene must be collected along with evidence collected from the victims.
Once the investigators have determined the type of bomb and the police enter it into the FBI’s Terrorist Explosive Device Analytical Center database and cross analyze the bomb. The TEDAC is a base where all homemade explosive devices that are used by other bombers is reported. This data base helps identify if the bomb is signature and related to others. Terrorist groups use similar designs and common ingredients which help to link different bombs together. If the explosive is found in the database, it may be possible to link the type of bomb to another case .
In some cases the bomb is unique, and it may be possible to determine where it was bought based on things it was made of. Taggots are chemical markers found inside certain bombs that identify where the explosive could have come from. TNT is an explosion that can’t be bought, if TNT is found to be the type of bombed used its likely that it was stolen and may be traceable. To acquire information about explosives that have been stolen there is the mandatory theft reports that are filed by the Bureau of Alcohol, Tobacco, Firearms and Explosives which can be helpful identifying stolen explosives (Wickman, n. d).
The bombs with more power and softer casings tend to leave smaller fragments than bombs with harder casings. Small fragments are useful to the investigators in many ways. One example of small fragments leading to the identification of bomb was the case of Pan Am Flight 103. Investigators found a fragment of a circuit board in a burned shirt left behind. The fragment of the circuit board proved to be a vital piece of evidence. In cases with small fragments may help the investigators identify what the bomb was constructed with, such as the type of watch used as the timer of the bomb, or the glue, tape, or pipe used to make the bomb (Wickman, n. ).
Larger fragments from low explosives such as pipe bombs can leave behind fragments several inches long. In some cases the cap of the pipe bomb will just explode leaving behind the rest of the bomb behind. On larger pieces of evidence it is easier to find finger prints or DNA evidence that was left behind. Finger prints are lifted from fragments left behind investigators use “superglue fuming”. “Super fuming” is when investigator heats superglue in a losed vessel with the piece of evidence inside, and the superglue forms around the fingerprint, emphasizing and preserving it, super glue bonds well to sweat and residue left behind from human finger prints.
High explosives and homemade explosives don’t leave behind finger print the explosion is to hot and any finger prints left behind would be burned off during the explosion, so investigators will look for DNA evidence to link the bomb to the bomber. Touch DNA, is when DNA is left behind containing dead skin cells. Depending on the ability to retrieve the touch DNA evidence it may be possible to link the suspect (Wickman, n. ).
Some other ways the investigators can link the bomb back to the bomber are by simpler kinds of evidence. Evidence such as a bag or backpack or clothing left behind may contain valuable information, all items behind should be tested for trace evidence such as fibers, hairs to help determine where the bomber came from, or where the bomb was made. A cell phone or a similar object left behind and should be collected and analyzed; the cell phone may be the source of the detonator or contain valuable information about the place the bomb was made or other suspects in the bombing.
All of the different ways listed about are different ways to connect the bomber to the bomb by the use of identification of the bomb, traces from different types of evidence left behind, or possibly by finger prints or touch DNA (Wickman, n. d). There are numerous explosion cases where physical evidence such as finger prints, DNA, specific materials to make the bomb, or photographs of the bomber were used to connect the bomb to the bomber.
Below are a few cases in which evidence collected from the scene linked the bomber to the bomb, and or to other similar bombings. One of many specific cases where the bomber was identified based on DNA evidence found on the bomb led to the identification of Najim Laachraoui, A veteran Belgian combatant and bomb-maker for the Islamic State. His DNA was found on two of the explosives belts used in November of 2015 in Paris and has been linked as of the suicide bombers in the attack in Brussels (Henley & Chrisafas, 2016).
