Gunpowder Residue and Analysis - Essay Example

Forensic Evidence of Gunshot Residue using Colorimetric Techniques and SEM-EDX You're Table of Contents I. Introduction: Gunpowder Residue and Analysis II. Background into How Residue from Gunpowder forms and Breakdown of Evidence III. Scientific Evidence and the Methodology in the Analysis of the Gunpowder Residue IV. Thorough Description of Specific Tests that are Utilized V. Conclusion Abstract In the various forensic studies on determining the presence of gun powder residue, several tests can be chosen but only one will be specified to be used. This literature is involving a thorough discussion into the relevant studies utilized today. Also, there is inclusion as to how the evidence is gathered, how determination is reached in specifying the shooter, the time barrier that is encountered within gun residue studies, uniformed protocols, and much more pertinent information, to bring a better comprehension into the area of forensics when evaluating traces of gunpowder residue. This proves very crucial to many investigations, especially when attempting to reach a logical conclusion of whether or not the investigated shooting was done in self defense, suicide, or in fact a homicide. Again, all the most up to date studies are also included in this researched literature being presented. The conclusion is in showing just how valuable of an asset these specific tests really are towards the outcome of numerous investigations from the past and in the present. You're Name Professor Course 8 January 2006 Forensic Evidence of Gunshot Residue using Colorimetric Techniques and SEM-EDX Introduction: Gunpowder Residue and Analysis The materials that are found to make up gun powder residue and seemingly found to predominantly consist of a mixture including organic and non-organic substances are basically elemental metals, among other items. However, it has been determined by a number of forensic analysists that only the materials involving primarily metallic residues are the most applicable to be used in testing procedures (RML 2004). There are also specific types of metals found in the residue left behind by a gunshot that are more detrimental than others. These metals are found to be highly sensitive to forensic tests and consist of: lead, antimony, barium, and sometimes copper is another one of the metals that is attempted to be obtained as well. The reason for analyzing gunpowder residue and the various other elements traceable in it proves highly beneficial in investigations where a determination of homicide or self defense is in question. The most commonly used tests that are carried out on these metallic materials are atomic absorption or AA and also microscopy with energy dispersive X-ray analysis or otherwise popularly known as the renowned SEM/EDX test (RML 2004). Past experiences within the extensive testing areas have shown that the secondary method proves to be the most reliable and conclusive in validating pertinent data to prove a case. However, the negative of choosing one over the other is the fact that once one of these methodologies have been chosen and implemented, the other test would be useless to incorporate as well due to the evidence already having been affected by the previous test. This can pose problems, especially if the chosen test does not prove to find any reliable data or present with results that would help the case. Basically, the whole process would have to start again with trying to gather more field data from the crime scene and hopefully finding enough residues to utilize a new test and come up with better results. However, the SEM/EDX has always proven very worthy for investigators although it is the more expensive test and takes up a considerable amount of time to return the most accurate results. Using any one of these methods, there is often a reasonable determination reached in regards to the pattern of the gun powder residue left on the target and evaluating how close the muzzle of the weapon must have been in proximity to the target. This often sheds light on whether the questionable actions of the supposed suspect were intentional or were carried out solely for self defensive purposes. Background into how Residue from Gunpowder forms and is analyzed It has been found to be the remnants of traces of gunpowder residue that has more often times than not lead investigators to the person responsible for the shooting. The reason for this is due to the fact that when an individual holds a firearm and actually fires it, the gunshot residue is somehow left on the suspect's hands as well as in the vicinity of where the crime took place (Aaron 2005). What takes place when a gun goes off is that the high intensity explosion from the cartridge completely burns much of the gunpowder. It has often been believed that due to this there is no concrete way for investigators to be able to gather enough of a quantifiable amount of the residue to trace anything back to the shooter. This might have been the case years ago but in present day, thanks to the many advancements in technology, many very valuable scientific tests have developed in the area of forensics, that all began from discovering how diphenylamine can be used to trace small amounts of residue left behind and normally unseen to the naked eye (Aaron 2005). This test was formally known as the 'paraffin test' but is hardly used any longer due to the idea that many nitrates are not guaranteed to provide enough specificity as well as the knowledge that this type of testing takes rather large deposits of nitrites in order to develop a correct color analysis. However, because this test was utilized quite often in years past it is still referred to when discussions about analysis of GPS comes up among forensic scientists. Unfortunately, GPS does not stay on a suspect's hands and clothing indefinitely due to the make up involved with it. It is somewhat like chalk so when you rub your hands it wipes a little more off every time and when hands are washed it practically washes any signs of residue away. If clothing gets washed it is very hard to determine any lasting traces of gunpowder on them, this is why time is impeccably important in shooting cases in order to gather every possible bit of evidence to make a solid case. Therefore, these types of tests are not as easy as they seem and normally it takes other gathered evidence combined with these tests to ultimately lead to an arrest. Even though there is some negativity to be found in the methodology of these tests they are still considerably reliable to the assistance of cases involving shootings. One main point of thought and fact that either test can prove is that there was in fact a weapon in the ands of the person or persons responsible for the shooting. This is proven whether gun powder residue is found on the suspects hands or not. Also, simply because traces of residue are found on someone's hands does not necessarily mean that they were the one who fired the weapon. They could have just held it or loaded the ammunition. These to actions leave traces of residue as well. What is for certain in these specific testing methods is that consistency and timeliness are essential in gathering appropriate data to determine a solid case. There are certain conditions that must be met to ensure accuracy in the proper gathering of the residue for the analysis (Aaron 2005). Also, investigators have implemented the following guidelines to make sure valuable time is not wasted as well as resources are being used effectively. If the following is assumed to be evident at the time the investigation is ongoing then the test chosen will not be carried out. The guideline is as follows: The person can be associated recently with a firearm by a witness The hands were washed or more than a few hours have elapsed since the shooting The ammunition used in the shooting does not contain both barium and antimony (Aaron 2005). By following this protocol a myriad of misunderstandings can be avoided and again, since time is of the essence it eliminates unnecessary processes in the area of GSR testing. Scientific Evidence and Methodology in Analysis of Gunpowder Residue As has been previously mentioned in this literary research, gunshot residue includes the elemental metals of antimony, barium, and lead that all are intertwined with the process of a weapon being fired and trace materials being left behind. These metals are what are found to be consistent in the blow-back after firing a weapon (Harbert 1993). A determination has been made that the quantity of gunpowder residue that is found to be left behind has a good deal to do with the type of weapon that was utilized. It has been well recognized that a revolver will most assuredly produce more GSR than a.38 caliber weapon so therefore these tests also pinpoint exactly what type of relevant weapon is found to be associative with the shooting simply based on the quantity of gunpowder residue (Harbert 1993). In the realm of utilizing the Atomic Absorption GSR test, the chemist is specifically searching for traces of antimony and barium. These two elements are hardly ever found in the natural environment but they are very common attributes of the cartridge primers of firearms (Harbert 1993). What is actually attempting to be verified in this test is the ratio of these two metals in variation with one another. It is this ratio that determines whether or not the test will show any positive results for signs of gunpowder residue. If it does it proves that the firearm would have been discharged recently which gives higher probability that the weapon being tested is the one that was used in the criminal shooting being investigated. There are critical levels of testing that are implemented in the GSR process and these are known as, 'thresholds'. One certain threshold is what is used to determine the control discharge study and the hand blank analysis (Harbert 1993). There are specific ways the chemists and analysists conduct these studies. Some of these might have been previously mentioned but will still be included in the following bulleted paragraph. Atomic Absorption testing searches for a threshold as a primary starting point The laboratory defines a uniform threshold for chemists to adhere too The tests are highly recommended to be completed using specific lab equipment Chemists attempt to ensure their tests remain accurate by having updated equipment and a consistency in the procedure that was utilized In order to present the most competent and logically validated evidence to support a case, scientists have to ensure all protocols are followed precisely and in the proper order for tests to give 100% certainty in showing any form of gunpowder residue. Specific Tests Utilized in Gunpowder Residue Analysis The Greiss Test It has already been clarified that 'evidence that a person has fired a gun provides a link in the chain of proof in shooting investigations' (13th Interpol 1998-2001). The Greiss test itself used to be a very popular means of detecting organic nitrite compounds until it was proven that this specific test is not always accurate and also has a bad habit of providing false positivities which has not bode dwell for shooting investigations (Wikipedia Encyclopedai 2005). The test uses a chemical analysis method, incorporating the chemical of ether and dividing the sample into two bowls. Subsequently, hydrogen peroxide is added to the initial bowl then the greiss agent is mixed in as well. This provides a color coded type of evidence, determining whether the presence of nitrites is positive or negative. If the solution turns pink it is vindictive of the presence of nitrites. Finally the complete test can be totally proven to be accurately positive if the secondary bowl remains clear of color after the greiss reagent is added. However, this test has not been readily used by British police since the mid 1980's due to its ability to detect chemicals which aren't directly relative to determining the traces of gunpowder residue and which can create a misinterpretation in the readings of the test (Wikipedia Encyclopedia 2005). Fluorescent Lighting Testing This type of testing was well known even back in the 70's although different methods were used to gather the evidence. The Royal Canadian Mounted Police used what was known as water cooled argon ion lasers but then they were bulky and extremely expensive (Melles Griot 2000-2002). Now, in present day, omnichrome units are used which utilize a high intensity incandescent bulb that sets off a myriad of wave lengths to determine the presence of fingerprints on items that have traces of gunpowder residue. These would not normally be detectable any other way and it provides fast and reliable results. This type of testing eliminates the need for chemical agents as various fluorescent colors make otherwise invisible evidence become visible, as was previously stated. The main type of investigation this is used for are those trying to get a correct print off of a gun. Sandia Gun Residue Detection Technique This is a relatively new test but already is making a marked difference within the outcome of shooting investigations. This technique utilizes the materials left behind from the blow-back from the gun. The most important details about this technique are how fast it can be done and how reliable the results are. A suspect can be swabbed for gunpowder residue directly at the crime scene and results come back almost instantaneously, providing efficient and precise timing, something that has been a large concern in the past (Sandia National Laboratories 2002). The process is very simple and involves using a fiberglass swab which is rubbed on the various areas of the suspects body that could have came into contact with the gunpowder. It is then placed in a plastic cube, a button is pushed and a stopper inside the vial busts a little flask which then releases a clear chemical agent. This in turn soaks the swap and a chemical reaction exudes. If the result is positive it will turn blue if not it will remain the same color. The test result is received in exactly one minute and provides the necessary evidence in some cases to go ahead and press charges to make a legitimate arrest (Sandia National Laboratories 2002). Sodium Rhodiazonate Testing: This test is found to be very useful when attempting to determine if there is a presence of lead left in the discharged materials from various firearms (Bartsch, et al 1996). By making sure that the chemical, 'sodium rhodizonate' is stored below a PH3 level, it is diprotonated which then allows for the formation of rhodizonic acid, hence this solution will be able to increase its amount in a time area of one to ten hours and be ready for appropriate usage in forensic testing in gunpowder analysis. This newer process does away with prior problems that were found with it such as improper color coding analysis. When the desired scarlet complex is seen then it verify's the presence of lead, validating the fact that a firearm had been discharged (Bartsch, et al 1996). SEM/EDX: There have been found to be various issues when using this form of testing to analyze gunpowder residue. On in particular is in regards to the excessive time that is needed just too properly search and identify traces of various metals from blow-backs of firearms (Tillman 1987). What SEM basically does is an automatic process which searches for: correct particle sizing, chemical typing, and spectral acquisition. It also can save all gathered data to a disk format which can then be accessed for a later review and verification process (Tillman 1987). There are also a myriad of handgun that have proven to bring consistent results using a tape lift method. These are: .32, .38, .35, and .22 caliber handguns. By utilizing a tape lift method, investigators and analysists perceive it to be considerably more time efficient and resulting in excellent reliable collection ability compared to the SEM/EDX method (DeGaetano, et al 1992). In conclusion, the literature presented has very thoroughly shown how crucial these types of tests are to criminal shooting cases. The courts do allow the admittance of this type of evidence as long as both legal sides get a chance to review all documented materials submitted as evidence to the court in the case. However, forensic experts are questioned as to their qualifications, the methods used to obtain the results, the quality of the testing and the quality of equipment used, and quite a few other questions in order to validate the authenticity of the testing and the provided evidence. All in all though, forensic testing on gunpowder residue has lead to the arrest and conviction of many known suspects involved in shooting cases. As technology advances these techniques prove more reliable and highly more accurate than in predeceasing years. Cited References 1. Aaron, Roger (2005). 'Gunshot Primer Residue: The Invisible Clue' Retrieved From: http://www.hackcanada.com/blackcrawl/survive/gunshot.txt Accessed on: 6 January, 2006 2. Bartsch, MR & Kobush, H.J. & Wainwright, K.B. (1996) 'An update on the use of the Sodium Rhodizonate test for the Detection of Lead Originating from Firearm Discharges' Journal of Forensic Sciences, Vol.41, Issue 6 3. Degaetono, D & Siegel, J.A. & Klomparens, K.L. (1992) 'A Comparison of Three Techniques Developed for Sampling and Analysis of Gunshot Residue by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis' Journal of Forensic Sciences, Vol.37, Issue 1 4. Harbert, James (1993). 'A Guide to Gunshot Residue Analysis for the Criminal Defense Investigator/Attorney' Retrieved From: http://www.jwharbert.com/gsranalysis.htm Accessed on: 7 January, 2006 5. 13th Interpol Forensic Science Symposium "1998-2001). 'Firearms Report Review Paper' Retrieved From: http://www.interpol.int/Public/Forensic/IFSS/meeting13/Reviews/Firearms.pdf Accessed on: 7 January, 2006 6. RML (2004). 'Serology' Returned From: http://www.rockylab.com/SEROLOGY.html Accessed on: 7 January, 2006 7. Tillman, WL (1987) 'Automated Gunshot Residue Particle Search, and Characterization' Journal of Forensic Sciences, Vol.32, Issue 1 8. Wikipedia Encyclopedia (2005). 'Greiss Test' Retrieved From: http://www.wikipedia.org/wiki/Greiss_Test Accessed on 6 January, 2006 9. Melles Griott (2000-2002). 'Forensics Tutorial' Retrieved From: http://www.mellesgriot.com/products/forensics/forensicstutorial.asp Accessed on: 7 January, 2006 10. Sandia National Laboratories (2002). 'Sandia-Developed Field Kit Helping Nations Police Departments Solve Real Crimes' Retrieved From: http://www.sandia.gov/news-center/news-releases/2002/tech-trans/isid.html Read More