| Friday, June 29, 2007 marked another day in | | | | shock. |
| London's history in which a terror scare | | | | |
| rocked the people of this city. Fortunately, | | | | - Initiating explosives are highly sensitive |
| nobody was hurt unlike the last bombing that | | | | to these effects. Because of their |
| struck a London public transport system | | | | instability, home-made bombs rarely use |
| nearly two years ago next week. Two car bombs | | | | initiating explosives. These explosives are |
| were discovered and quickly defused by a | | | | usually found in primers and blasting caps, |
| Scotland Yard bomb squad. Now the hunt goes | | | | where they initiate other more stable |
| on to find the perpetrators who could have | | | | noninitiating explosive reactants. Mercury |
| caused such mass destruction of innocent | | | | fulminate and lead azide are widely used in |
| lives. | | | | this manner. |
| | | | |
| If these car bombs did explode, how do | | | | - Noninitiating explosives are more stable |
| forensic criminal investigators go about | | | | and commonly used in military and commercial |
| evaluating this particular crime scene? In | | | | applications. Examples of these explosives |
| this article, we will attempt to explain how | | | | include dynamite, trinitrotoluene (TNT), |
| the investigators evaluate explosive | | | | pentaerythritrol tetranitrate (RDX), and |
| situations, how they define explosives, and | | | | cyclotrimethylenetrinitramine (PETN). ANFO, |
| how they go about investigating a bomb scene. | | | | an easily made explosive material, is a |
| | | | mixture of ammonium nitrate and fuel oil. |
| Explosions and fires are similar chemical | | | | |
| reactions that take place since both result | | | | Ammonium nitrate is an oxidant loaded with |
| from the consumption of fuel and oxygen. The | | | | oxygen and can be found in fertilizers. Bombs |
| only difference between the two is that an | | | | made from this material were used in the |
| explosion reaction occurs faster than a fire | | | | Oklahoma City and 1993 World Trade Center |
| reaction. Explosion reactions use up their | | | | bombings. |
| fuel such as gasoline or gunpowder almost | | | | |
| instantaneously partly because the materials | | | | Investigating a Bomb Scene |
| are confined to a small space. Fire | | | | |
| reactions, on the other hand, consume their | | | | Looking through the scene of an explosion |
| fuel such as wood, trees, or paper more | | | | requires the same attention to detail as does |
| slowly than explosion reactions. If you | | | | a search of a fire scene. Searching for |
| ignited these materials in an open space, the | | | | remnants of an explosive device such as the |
| materials simply burn. In contrast, if you | | | | igniter and timer may be important in |
| tightly pack these same materials into a | | | | determining the type of explosive used and |
| container, it explodes when you light it up. | | | | the persons responsible for this crime. |
| | | | Furthermore, forensic criminal investigators |
| Explosions pose problems for investigators. | | | | focus their searches on gathering debris to |
| The explosive device and any surrounding | | | | test for unexploded residue, which is almost |
| structures are heavily damaged if not | | | | always present. |
| entirely obliterated. Unless a secondary fire | | | | |
| occurs, investigators can usually ascertain | | | | Microscopic examination of the debris may |
| the point of origin with no problem. Finding | | | | unveil black powder, gun powder, or both of |
| fragments of the device, timers, or igniters | | | | which are easily recognizable by the color |
| is another story. | | | | and conformation of their particles. After |
| | | | conducting a microscopic inspection of the |
| Explosives are categorized as either high or | | | | debris, the lab technician rinses the debris |
| low according to the speed of their resulting | | | | with a solvent, usually acetone, and then |
| shock wave. Low explosives usually move at | | | | analyzes the resulting solution, using |
| rates of up to 1,000 m/s, and high explosives | | | | various scientific laboratory techniques such |
| may reach speeds up to 8,500 m/s. | | | | as thin-layer (TLC) or gas chromatography |
| | | | (GC) and mass and infrared spectroscopy. |
| Black powder and smokeless gunpowder are the | | | | Determining the identity of the explosive is |
| most readily available and commonly used low | | | | made through a combination of these |
| explosives. A mixture of table sugar and | | | | techniques. |
| potassium chlorate makes another easy | | | | |
| explosive. Bombers do not need to be complex. | | | | After determining the nature of the explosive |
| | | | used, criminal investigators then target |
| High explosives can be divided into two | | | | their investigation on the seller and buyer |
| categories all dependent upon their | | | | of that explosive. |
| sensitivity to heat, friction, or mechanical | | | | |