Scanning Electron Microscope - Research Paper Example

RESEARCH PAPER College: A scanning electron microscope is a microscope that generates image samples when scanned by a directed beam of electrons. It works under the principle that free electrons in the sample produce various signals that can be detected. Generally an image is produced by combining the beam`s position and the detected signal after the electron beam has been scanned in a raster scan pattern. After heating the filament, a high-energy electron beam is produced after forcing the electrons down a column, focusing them to a very small diameter beam. As the high electron beam penetrates into the sample, numerous interactions of electrons occur. This makes the electrons from the atom containing the sample to be ejected from their orbits around the atomic nucleus making them possible to be detected by SEM. An extremely high-resolution image on the SEM computer monitor is generated due to the ejected electrons, which is also capable of tremendous magnification. A set of X-ray whose energy vary, and which arise from the energy released when an outer shell electron replaces an electron knocked out of its inner shell by focused beam, is detected. The operator of the SEM can identify the elemental makeup of the spectrum. This is done by examining the spectrum on the computer monitor (Forensic Science Society, 2011). The ability to generate image samples has made it possible for scanning electron microscope to be applied in a broad field. This include activities such as research and even in cases that involve detecting gunshot residue, which is the chemical compound, and particulate material that results when a firearm is discharged. This can be used to determine whether the case will be viewed as a homicide or a suicide case. The gunshot residue composes both the primer and powder of the cartridge by default. The typical characterizes of a gunshot primer are: They are typically in the range of 1 to10 micrometer in size, most primer consist of leadstypnate which acts as an initiative explosive, barium nitrate which serves the purpose of an oxidizer and the primer particles are spheroid in nature. After a gun has been shot, the residue may remain on the body, on the clothing of the person who fired the gun, it may remain on the surface of the victims wound or on other target material present at the scene where the gun was shot. When SEM is used to scan the electrons that are available on the chosen sample and high amount of lead, barium, or antimony are detected (normally the core elements in the primer) it is concluded that there exists a gun residue on the scanned sample. On the contrary, if electrons of other common metals like aluminum, sulfur, tin, calcium, potassium, chlorine, copper, strontium, zinc, titanium, or silicon are detected then further scanning has to be done to bring out the exact appearance of the particle containing the electrons of this metal so that it can be distinguished from gunshot residue by SEM. SEM has greatly helped in the police forensic department to determine whether a homicide or a suicide occurred when a body of a dead person is found. This is achieved by studying the gunshot residue after it has been scanned using SEM. When residue of the gunshot are not found on the hand of the dead body then the forensic department will indicate in their report that, there is no prove that the person in subject committed suicide. The detective is therefore given a green light to start investigating on the murder of the dead body. Incase the gunshot residue are found deposited on the hand of the dead person the case will most likely be considered as suicide. Although the judiciary system will now require more evidence, it may argue that there is a chance that the person was found dead. Due to these shortcomings in the forensic department, the judiciary system established a body; `The Scientific Working Group for Gunshot Residue (SWGGSR) so as to uphold the integrity and honesty of the forensic department to enable the general public to be able to trust the report that will be presented by the forensic department. The main purpose of the SWGGSR is to come up with internationally accepted standards and guidelines for the forensic examination of gunshot residue. Some of the guidelines included analysis of gunshot residue by SEM automatically and manually, making recommendations concerning the report that the forensic department should come up with, issues concerning contamination of the scene to be scanned, indicating when to accept or reject evidence delivered by a witness. SWGGSR also dealt with training the personnel working in the forensic department to minimize the errors that were made by those working in the department. The formation of SWGGSR has enabled the forensic department to achieve some of the core value of integrity, which comprises of honesty, poise, patience, determination and patience. Under honesty, the forensic department has encountered challenges because the reports sometimes are rendered useless as one might argue that the sample presented to be analyzed was contaminated especially if he or she presents enough evidence to support the claims. When it comes to poise, the forensic department has been able to maintain calmness among the public if their exist a sample to be scanned using SEM as they believe that the result will bring out enough evidence to see the case progresses to new heights. When it comes to patience the forensic department faces, a lot of criticism as to why sometimes they take excess time in presenting their report and this is because those who are not in the forensic department don’t understand that there are same samples that must be keenly scanned and rescanned to give perfect results. As long as determination is concerned those in the forensic department are usually determined to make sure that the result they present after using SEM is accurate and reliable by being kin and effective when preparing the sample to be used in SEM. When it comes to passion, the public has developed an intense emotion and feeling as to the technology revolving around the examination of gunshot residue using SEM as they find it interesting. For efficient production of X-rays in analytical SEM, the electron must be of high current density. Normally there are three main systems for generating electrons in SEM to be used in analytical system, namely; tungsten filament, lanthanum hexaboride filament and field emission gun. Although lanthanum hexaboride filament and tungsten filament provide extended filament life and stability with superior image resolution as compared to that of tungsten filament, they all happened to be suitable for both manual and automated GSR analysis. The judiciary system requests to know the procedure that was used to sample GSR on the scanned part so as to decide whether they will use the report from the forensic department or not. When the sampling is done from a human subject the judiciary encourages the forensic department that whenever possible they should sample from the subject prior to handcuffing. The subject to be sampled should be under close observation before sampling and the forensic department should not allow the subject to wash his or hands until the sampling procedure has been done away with. The subject should also not be allowed to put hands in the pocket as this may wipe away the GSR and the subject must not be finger printed before the GSR collection. If all these are found to have been observed by the forensic department, then there is a high chance that the judges will accept to use the report as liable evidence in the case. Otherwise, if it is found that some procedure was not followed then the judiciary system may decide to dismiss the report and findings presented by the forensic department. When the report comes back from the forensic department as negative, indicating that the human subject sampled has no GSR residue on his or her hands then they further inquire whether the sampling was done thoroughly. This is done by determining if the sampling was done on the back of each hand including the thumb and the forefingers. In addition, they expect the sampling to have been taken from other parts of the body including forehead, cheeks and neck, which is done using adhesive sampling stubs. After all this has been clarified then the jury may decide to clear the sampled person or recommend the subject to be further investigated (Saperstein, 2001). When the subject sample is collected from materials such as clothing, vehicles or any other material the jury has laid down procedures to be followed to accept the report from the forensic department as evidence. This pertains when it comes to cases involving scanning of gunshot residue using SEM. This procedure involve; making sure that the equipment to be used during sampling including SEM are kept in a controlled environment free from contamination and that SEM is protected from exposure to GSR residue during the examination process. The forensic department should avoid collecting sample from sights that are likely to be contaminated; samples should be taken as soon as possible to avoid loss of evidence or contamination. The jury also insist that the storage area should be clean and of high maintenance to to preserve the integrity and continuity of the sample. Although SEM has made it possible to detect gunshot residue on hands, clothes and other objects, hence helping in convicting bloody murderers, it has also convicted innocent people who never deserved to be behind bars and cleared murderers now roam free within the general population. Due to this, the judiciary system has highlighted the advantages and disadvantages of the technology of gunshot residue using SEM to the forensic department of police, which they should always consider when writing their report after analyzing and studying the results that they got from SEM. Some of the advantages are that a shooter can be sampled even after eight hours, so it is not necessary for an offender to be caught red handed on the scene. If the person who did the act of shooting washes or wipes his or her hands so as to dodge the SEM from detecting the gunshot residue on the surface of the hands , it would still be possible to detect the gunshot residue on the clothing that was on his or her body. The disadvantages are that gunshot residue can be easily removed from the hand of the shooter due to their microscopic sized particles by putting hands in the pocket or even rubbing hands together. It may also not be able for SEM to detect gunshot residue on a person’s hand after a long period like one week. SEM can detect combination of lead, barium and antimony on a subject sample leading to the forensic scientist to indicate on the report that the person had fired a gun while in real sense they are deposits, which arise from other sources like commercial firework, airbags and even brake lining, which might blind the jury when giving their verdict. Gunshot residue can be transferred from one person to another, which has made it hard for the jury to pass their verdict as one may deny to have fired any gun even if the results from SEM show it. If a number of people are scanned using SEM and are all found positive with gunshot residue, there may be almost zero chance to know who fired the gun on the discussed homicide or even to determine which gun was used. The governments should try to embrace the technology of using SEM to detect gunshot residues, as it is capable of detecting even the smallest particle that is on a sample. SEM helped solve the complex and twisted case ‘People V. Robert Blake’ where he was accused of shooting his wife twice, Bonnie Blake, while she was sitting at the passenger side in Blake’s car. The conclusion therefore is that, after the sample has been analyzed and recorded the forensic scientist should make a step further to know the background of the person or people and to work with the probability of contamination before writing an official report so as not to misguide the jury. This will help to uphold the integrity and honesty of both the judiciary system and the forensic department Case study The people V. Robert Blake Robert Blake a former star in the media industry was accused of shooting his wife two times and killing her on the spot. It was evident that the shots had come from outside the car that his wife was sitting in at the passenger seat. Blake told the investigation police that during the time her wife was shot, he was sitting in the driver seat of the car and that he only realized that his wife had been shot some minutes. He also confessed that at the time of the shooting, he had his pistol with him but the police later confirmed that the pistol was not the murder weapon. However, GSR was found in his hands and clothes. The gunshots residue that were present in his hands and clothes were presented to the court as evidence. The murder weapon that was presented to court was the World War II 9mm pistol that the police later retrieved in a dumpsite near the location of the shooting. On 2 November 2001, the murder weapon was fired with the objective of finding out if the gun left behind any GSR on the hand of the shooter. This was to enable the investigators to make a conclusion on the evidence that SEM had presented to the court from Mr. Blake. The investigators wanted to determine if there were any connections between the two. The gun left behind GSR and the SEM results on the test victim was exactly similar to the results from Mr. Blake’s hands. This was clear evidence that Mr. Blake had shot the same gun and very clears evidence that was presented to court. However, his lawyers argued that the composition of the GSR on Mr. Blake’s hands and clothes had not been considered and so the results would be unfair since his pistol also had GSR. Before firing however, the pistol had been inserted in alcohol. This was done as a precaution to the two CCI. However, some analysis data was not presented to the public after the court ordered that they be kept private. This included the reason why the investigators had opted to use lead free bullets during the test shot (Mazeika, 2010). From the above information, it is evident that SEM has been very useful in solving various crimes. Without SEM, many murderers would go unpunished since there would be no evidence linking them to the crimes. It is therefore a requirement that the justice system should ensure that they always follow the right steps during the gathering of evidence so that faulty results are not presented to court. References Forensic Science Society., California Association of Criminalists. & Forensic Science Society. (2011). Journal. Harrogate, Yorkshire, England: The Society. Mazeika, D., Bartholomew, B., Distler, M., Thomas, K., Greenman, S., & Pratt, S. (January 01, 2010). Trends in police research: a cross-sectional analysis of the 2000-2007 literature. Police Practice and Research, 11, 6, 520-547. Saperstein, R. (2001). Criminalistics: An introduction to forensic science. Upper Saddle River, N.J: Prentice Hall. Read More