forensic science - gsr trace
When an officer arrives at the location of an alleged shooting, after first rendering aid to the victim, he or she begins to search for evidence. Much of this effort consists of searching for the bullet, the gun, shell casings, and witness testimony; however, when the shooter leaves the scene, he/she takes with them a substantial part of the evidence that can significantly improve the prosecution's case. This evidence can be found on the hands, body and clothing of the shooter. Much of this evidence may be invisible to the naked eye, yet is still valuable for the prosecution's case. This evidence includes micro blood splatter, trace metal evidence, gunpowder residue, and even the gun. The first step when a suspect is apprehended in a shooting is to frisk the suspect for the weapon. While this will display that the suspect has a gun after the approach, it does not assist in the safety of the officer beforehand, nor assist in screening large quantities of people. Being caught with the proverbial smoking gun can be damning evidence in court, but typically at a crime scene, many onlookers gather making the frisking of each individual at the scene or leaving the scene an impossibility. In 1995, the Justice department fund
Gas chromatography takes these samples and vaporizes them causing the atoms present to become gaseous. Usually the resulting vapor is mixed with a light gas, such as hydrogen or helium, to help dissipate the sample. The sample is then submitted to mass spectroscopy (usually a part of the same machine) where the sample is subjected to an electron bombardment where individual atoms of the sample are dislodged. These atoms travel different courses through the electromagnetic field depending on their mass. This then allows the machine to determine the composition of raw materials within the samples through the quantities of these materials. 10,11
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Approximate Word count = 2507
Approximate Pages = 10 (250 words per page double spaced)
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