The Use and Significance of Stable Isotopes in the Study of Forensic Medicine - Term Paper Example

? The Use of Stable or Radio Isotopes in Forensic Science Total Number of Words: 4,000 Executive Summary The study of forensic science has gained importance particularly when it comes to the need to solve criminal cases. In relation to the study of forensic science, this report will purposely conduct a systematic review which aims to discuss the advantages of using stable isotopes as compared to the use of radioactive isotopes. Table of Content Abstract ……………………………………………………………………………………… 2 Table of Content ……………………………………………………………………………... 3 1. Introduction ………………………………………………………………………….. 4 2. Literature Review ……………………………………………………………………. 4 2.1 Basic Information on Stable Isotopes ……………………………………... 4 2.2 The Use and Importance of Stable Isotopes in the Study of Forensic Science …………………………………………………………… 5 2.2.1 Determine the Characteristics and Geographic Origin of an Object, Food and Water Substances, an Animal, or a Person .. 5 2.3.2 Used for Generating Forensic Identification Purposes ………. 9 2.3.3 Determine the History of Drug Use, Trace the Origin of Illegal Drugs, and the Identification or Detection of Counterfeited Drugs ………………………………………….. 11 2.3.4 Other Uses of Stable Isotope Profiling in Forensic Science …. 12 3. Research Methodology ………………………………………………………………. 12 4. Discussion …………………………………………………………………………… 13 5. Conclusion …………………………………………………………………………… 15 References ………………………………………………………………………………… 16 - 24 Chapter 1 – Introduction Isotopes can be defined as “atoms of the one element that differ in the number of neutrons present in their nuclei” (Lennard, 2012, p. 316; Benson et al., 2006). For many years, isotopes have been used in the study of forensic science. In fact, it all started when the uranium – a type of stable isotopes were separated through the use of mass spectrometry – also known as the isotope ratio mass spectrometry (IRMS) in 1939 (Lennard, 2012; Chang, 2010; Benson et al., 2006). With the use of technology, radioactive carbon isotopes were widely used to determine the age of objects related to archeology such as fossils and other organic materials (BioZine, 2013; Chang, 2010). The two types of isotopes are known as stable and radioactive. Basically, one of the differences between these two isotopes is that radioactive isotopes are isotopes that decay over time whereas the sable isotopes do not (BioZine, 2013). In general, forensic scientists aim to identify the suspect and determine how and when a crime was committed (Benson et al., 2006). In relation to the differences between these two isotopes, this study will first discuss some basic information with regards to stable and radioactive isotopes followed by analyzing how these two isotopes can be use in the study of forensic science. Chapter 2 – Literature Review 2.1 Basic Information on Stable and Radioactive Isotopes Among the five (5) common types of stable isotopes used in the study of biological products include carbon (12C or 13C), hydrogen (1H or 2H), nitrogen (14N or 15N), oxygen (16O, 17O, or 18O), and sulphur (32S, 33S, or 34S) (BioZine, 2013; Chang, 2010; Benson et al., 2006). As explained by Benson et al. (2006), each of these elements can either be classified as a “dominant light isotope” which include 12C, 14N, 16O, 32S, and 1H or “heavy isotopes” such as 13C, 15N, 17O, 18O, 33S, 34S, and 2H. Even though most of the carbon element is considered as stable isotopes, it is necessary to take note that 14C is actually considered as radioactive isotope (BioZine, 2013; Chang, 2010). In most cases, the age determination of radioisotope profile assumes that the element of carbon is “constant” and “chemically inactive” (Chang, 2010, p. 1943). (See Table I – Average Stable Isotope Abundances of Elements on page 5) Source: Ehleringer et al., 2008 With the use of IRMS, forensic scientists or chemists are able to measure the isotopic ratio of one or more elements; making the fingerprinting of stable isotopes possible (Lennard, 2012; Benson et al., 2006). In fact, the presence of more isotopes in an object increases the chances wherein the chemists or forensic scientists are able to distinguish the object more differently from other objects (Lennard, 2012). As compared to the use of radioactive isotopes, there are so many reasons why stable isotopes are more commonly used in the study of forensic science. First of all, the sources of stable isotopes are plentiful by nature (Chang, 2010). Likewise, due to the absence of radiation emission, stable isotopes are much stable and safer to use particularly when it comes to the handling process (Godin, Fay and Hopfgartner, 2007; Koletzko, Sauerwald and Demmelmair, 1997; Vogt, 1997). As a common knowledge, radioactive isotopes are at risks of decaying over a period of time (Investigating Forensics, 2010). Since radioactive isotopes are much riskier to use than the stable isotopes, the application of radioactive isotopes in the study of forensic science is much limited as compared to the use of stable isotopes (Godin, Fay and Hopfgartner, 2007). This explains why even though the process of analyzing stable isotopes is very expensive, a lot of forensic scientists still consider stable isotopes more useful as compared to radioactive isotopes. 2.2 The Use and Importance of Stable Isotopes in the Study of Forensic Science 2.2.1 Determine the Characteristics and Geographic Origin of an Object, Food and Water Substances, an Animal, or a Person The role of stable isotopes in the study of forensic science is very significant. In most cases, stable isotopes are used in the process of allowing forensic personnel to determine the characteristics and geographic “origin, purity, and manufacturing processes involved” in food and water (Lennard, 2012, p. 316). Environmental factors such as “continentality” and “temperature” can significantly affect isotope ratios (Kreuzer-Martin and Jarman, 2007; Kendall and Coplen, 2001). In the study of wildlife forensics, analyzing the stable isotopes is also necessary in terms of determining not only the movement but also diet and the origin of a person or an animal (Chesson et al., 2008; Bowen, Wassenaar and Hobson, 2005). By testing the properties of stable isotopes like hydrogen and oxygen in water, forensic scientists are able to tell whether or not the origin of water came from the United States, Fiji, or other countries like France or Germany (BioZine, 2013; Lennard, 2012). In the case of bottled water, Bowen et al. (2005) found out that the main source of water used in bottled water is preserved even after going through some purifying process. Depending on the ability of the plant to undergo the process of photosynthesis, the carbon isotope ratios in food can range between -30% to -10% (Ehleringer et al., 2008; Cerling, et al., 2006). This explains why the value of delta 13C varies between -25% to -10% depending on the dietary sources of animals (Bol, Marsh and Heaton, 2007; Bol and Pflieger, 2002; O'Connell and Hedges, 1999). (See Figure I – Carbon Isotope Ratios in Animals with Two Different Food Sources below) Figure I – Carbon Isotope Ratios in Animals with Two Different Food Sources Source: Ehleringer et al., 2008 When it comes to determining the origin of food sources of human beings and animals, forensic personnel can test the properties of carbon and nitrogen isotopes (BioZine, 2013; Lennard, 2012). Aside from determining the geographic origin of food and water sources, stable isotopes are also used in determining whether or not foods and beverages are pure or contaminated (BioZine, 2013). It simply means that the isotopic ratio of hydrogen and oxygen that is present in water and/or the isotopic ratio of carbon and nitrogen in different food sources significantly differs from one place to another respectively. (See Figure II – Map of Incoming Precipitation Values when Addressing Stable Isotope Variations of Plants, Animals and Microbes across Landscape that Use Water Source below) Figure II – Map of Incoming Precipitation Values when Addressing Stable Isotope Variations of Plants, Animals and Microbes across Landscape that Use Water Source Source: Ehleringer et al., 2008 After examining the isotopic composition of beef samples that has originated from Chile and Argentina, Boner and Forstel (2004) found out that the process of examining the chemical composition of isotopes such as hydrogen and oxygen can help forensic scientists or chemist to tell where exactly the origin of the beef samples and that “a 13C/12C ratio above -20 per thousand” is the limit for organic farming. Specifically the act of conducting stable isotope analysis (or the process of statistically comparing the chemical composition of stable isotopes) makes it possible for chemists or forensic scientists to determine the potential sources of food and water products (Chang, 2010). To help solve crimes or accidents, forensic scientists have the option to compare or match the stable isotope analysis with the victim’s DNA finger prints (Lennard, 2012). In the process of testing the stable isotopic ratios in hair, finger nails, or bone samples, forensic scientists can identify and tell the exact residence of a person (Lennard, 2012). Ehleringer et al. (2008) took time to analyze the oxygen and hydrogen isotope ratios of a horse tail hair from Virginia which was moved to Utah and eventually found out that there was a significant change in the horse tail hair’s delta 2H and delta 18O values before and after the horse was transported from Virginia to Utah. Specifically the study of Cerling et al. (2007) presented a model which summarizes the pools of tissue and the impact of diet to learn more about the turnover rate of amino acids in the actual sysntehsis process of keratin that is present in the hair. The synthesis of keratin process in the hair clearly explains the mechanics behind the geographic shift in the hair’s isotope ratios (Cerling et al., 2007). (See Figure III – Changes in the Horse Tail Hair’s Delta 2H and Delta 18O Values Before and After the Horse was Transported from Virginia to Utah below) Figure III – Changes in the Horse Tail Hair’s Delta 2H and Delta 18O Values Before and After the Horse was Transported from Virginia to Utah Source: Ehleringer et al., 2008 There are also cases wherein the forensic scientists are being challenged to test the chemical composition of paints that can be found in a crime scene. When it comes to analyzing the sable isotopes in white paints, Farmer, Meier-Augenstein and Lucy (2009) strongly suggest that the process of conducting the isotope ratio mass spectrometry (IRMS) is better than the process of conducting the traditional Fourier Transformed Infra-Red Spectroscopy (FTIR) due to the fact that the IRMS is capable of exploiting or examining other factors such as the geo-location of oils that were added in the alkyd formulation. In some cases, forensic scientists are requested to identify, compare, and contrast the chemical composition of adhesive tapes used in a crime scene (Horacek et al., 2008). To identify adhesive tapes of the same or different brand(s), Horacek et al. (2008) revealed that the process of conducting IRMS is very useful particularly when it comes to analyzing the signature of its stable hydrogen and carbon isotopes. The use of genetic identity alone is not enough to lead the forensic investigators to the right perpetrator. In the process of characterizing the microbial agent(s), forensic scientists will be able to accurately identify and convict people who are responsible for a crime (Budowle et al., 2005a; Budowle et al., 2005b). In fact, the results of microbial forensic can be use as an important information or evidence when investigating a case in the courtroom (Kreuzer-Martin and Jarman, 2007). There are also cases wherein forensic scientists or criminologists failed to identify the body of a dead person using tooth analysis, finger printing analysis or a DNA analysis. In this case, Rauch et al. (2007) argued that the process of combining the process of analyzing the stable isotopic ratios of light elements such as carbon, hydrogen, and nitrogen with other heavy metals such as lead and strontium can help identify the country of origin of the dead body. 2.3.2 Used for Generating Forensic Identification Purposes Determining the geographical history of a person is necessary each time forensic scientists are trying to know more about a suspected terrorist or individuals who are suspected for smuggling or human trafficking (Fraser, Meier-Augenstein and Kalin, 2006). Basically, the process of conducting a stable isotope profiling is necessary each time the use of deoxyribonucleic acid (DNA) test (Radhakrishnan, 2011; Fraser and Meier-Augenstein, 2007; Benson et al., 2006; Fraser, Meier-Augenstein and Kalin, 2006) or fingerprinting test (Fraser and Meier-Augenstein, 2007) is not able to provide the forensic scientists with a proper identification of the subject (i.e. historical background, etc) or when there is a strong need for the local authorities to point out the history of a person (Fraser, Meier-Augenstein and Kalin, 2006). Based on the longitudinal study with regards to identifying the origin of a suspect, Fraser, Meier-Augenstein and Kalin (2006) found out that there is a high variation of hydrogen and oxygen found in the hair scalp and fingernails as compared to 13C/15N whereas the values of 18O and 15N in the fingernails are much higher as compared to the hair scalp. Based on the continuous-flow isotope ratio mass spectrometry (CF-IRMS) result, Fraser and Meier-Augenstein (2007) found out that there is a strong correlation between the values of delta (2)H in meteoric water and hair but not in fingernails. The use of mass spectrometry makes it possible to measure the isotopic ratios based on the mineralized dental tissues, har, scalp, or fingernails (Radhakrishnan, 2011). Likewise, Meier-Augenstein and Fraser (2008) revealed that there is a strong possibility wherein the gathered stable isotopic information can be useful in terms of being able to tell the origin of a dead body. However, each time there is a need to get the sable isotopic profiling of a dead person, it is more advisable to conduct a mass spectrometry test on the teeth. This argument is true because diagenesis or burial does not affect the dead person’s dentine or enamel more than it affects the bone minerals (Radhakrishnan, 2011). 204Pb is naturally stable whereas other stable lead isotopes such as 206Pb, 207Pn, and 208Pb “are radiogenic and produced by the decay of other elements such as uranium and thorium (SAHRA, 2013). A stable lead isotope analysis can be use in the process of generating forensic identification purposes (Gulson, Jameson and Gillings, 1997). For instance, Gulson, Jameson and Gillings (1997) conducted a pilot study based on the use of stable lead isotope analysis among the people who lives in the Eastern and Southern Europe and Australia particularly those individuals who lived in Lebanon, Soviet Union, United Kingdom, and the former Yugloslavia. After examining the teeth of the research participants, Gulson, Jameson and Gillings (1997) found out that the teeth of the research participants coming from different geographical locations have different lead stablility in their enamel which is subject to a 1% change each year. Basically, the research findings of Gulson, Jameson and Gillings (1997) strongly suggest that there was an exchange in Australian and European lead. Budd et al. (2000) also examined the lead content in human dental enamel. Using thermal and plasma ionisation mass spectrometry, Budd et al. (2000, p. 1) found out the “mean Neolithic enamel lead content is approx. 0.31 +/- 0.04ppm” and that lead exposure in modern people is 400 times more than the lead exposure of people during pre-historic time. After analyzing and interpreting the lead content in skeletal remains, Carlson (1996) found out that people with different cultural background are exposed to different sources of lead right after conducting chemical analyses of human tissues. 2.3.3 Determine the History of Drug Use, Trace the Origin of Illegal Drugs, and the Identification or Detection of Counterfeited Drugs Stable isotope analysis can also be conducted to determine whether or not a person has a history of illegal drug use (Zhang et al., 2005; Ehleringer et al., 2000; Ehleringer et al., 1999; Nakahara et al., 1990). For instance, with the use of stable-isotope dilution GC/MS method, a sectional analysis of methamphetamine can be performed on a drug users’ hair sample. After conducting the sectional analysis of methamphetamine test, Nakahara et al. (1990) found out that it is possible to conduct hair analysis test to determine the history of drug use of a person. With regards to determining the origin of illegal drugs, Zhang et al. (2005) mentioned that the use of delta(13)C is effective in terms of determining the origin of both morphine and heroin. For some reasons, some criminals are engaged in the use of illegal drugs (i.e. ecstacy, cannabis, ethanol, or LSD) or abuse of pharmaceutical drugs (i.e. sedatives, benzodiazepines, hypnotics, or anaethetics) (Kintz, 2007). Because of the chemical instability of the drugs or amensic properties which makes it easy for the traces of drug properties be cleared from the human body, Kintz (2007) explained that the process of undergoing urine and/or blood test may not always be accurate. Therefore, as a complement to blood and urine test, Kintz (2007) strongly suggest the need to use MS/MS technologies when conducting a hair sample analysis to test the suspect for the use of drugs in sexual assault. In case of counterfeited drugs, Santamaria-Fernandez, Hearn and Wolff (2009) strongly advice the use of either IRMS and/or the multi-collector inductively coupled mass spectrometry (MC-ICP-MS) method when analyzing the ratios of the following isotopes: C, N, S, and Mg. Basically, what the forensic scientists are expected to do is to compare the isotopic fingerprint of the genuine isotopic range as compared with the counterfeited drugs (Santamaria-Fernandez, Hearn and Wolff, 2009). 2.3.4 Other Uses of Stable Isotope Profiling in Forensic Science According to O'Connor et al. (2007, p. 282), “a person commits the criminal offense of arson when he or she starts a fire or causes an explosion with the purpose of destroying a building or occupied structure of another person”. In most cases, stable isotopic profiling can be performed to help solve crimes related to arson. For instance, match sticks can be recovered from the crime scene of a burnt place or subject. In line with this, Farmer et al. (2009) revealed that a stable isotope profile can be obtain in the matchstick since there is a strong possibility wherein the matchstick samples are not affected by the presence of chemicals coming from a fire extinguisher or petrol. Using the IRMS technique, Farmer, Meier-Augenstein and Kalin (2005) conducted a forensic case study to assess the contribution of using IRMS in identifying matchstick samples. Based on the research findings, Farmer, Meier-Augenstein and Kalin (2005) found out that “the maximum delta 13C variability observed within one box was 2.5 per thousand” which can create a very wide error margin to allow the process of differentiating the matchsticks. To be able to make full use of the IRMS technique when analyzing the stable isotope of safety matches, Farmer, Meier-Augenstein and Kalin (2005) strongly advice the need to examine the delta 2H values of the safety matches taken from the crime scene and the safety matches taken from the suspect. Chapter 3 – Research Methodology The search engine of PubMed and Google Scholar were used in this report. Key words and phrases such as: “forensic science stable isotopes”, “forensic stable radioactive isotopes”, “forensic isotopes origin”, “forensic isotopes drugs”, and “forensic isotopes personal identity” were used in search for related literature. To increase the validity and reliability of the synthetic review of literature, each of the gathered journals was thoroughly reviewed. Therefore, all journals that talk about the use of stable isotopes in relation to the study of forensic science were included in this report. All journals that are irrelevant to the main purpose of this study were immediately disregarded from the review of literature. Chapter 4 – Discussion – implications, sources, preservation potential, uses, biogeochemical message, advantages & disadvantages, need for research As a common knowledge, radioactive isotopes are chemically active whereas stable isotopes are “chemically inactive” (Chang, 2010, p. 1943). With regards to the differences in the chemical properties of both stable and radioactive isotopes, this report provided a clear explanation behind the importance of stable isotopes in the study of forensic science. In general, stable isotopes are “a signature for sample matching” (Kreuzer-Martin and Jarman, 2007, p. 3896). Unlike the use of radioactive isotopes, the process of examining or measuring the ratios of stable isotopes is a lot safer as compared to radioactive isotopes. Secondly, stable isotopes are also present anywhere in our environment. The fact that stable isotopes are easily found in the human body and our environment makes it a whole lot easier on the part of the forensic scientists to solve crimes using stable isotopes footprint. When it comes to measuring the stable isotopic ratio, several studies strongly recommend the process of conducting the IRMS technique (Lennard, 2012; Horacek et al., 2008; Benson et al., 2006) or the CF-IRMS technique (Fraser and Meier-Augenstein, 2007). For drug testing purposes, the use of GC/MS method is more advisable (Nakahara et al., 1990). The ratio of stable isotopes of water can be use in identifying the geographic origin of the water. After regressing the link between “dDf data sets and our dDp grids”, Bowen et al. (2005, p. 346) found out that “the hydrogen isotope tracer method has much greater predictive power than in Europe” at 95% as compared to North America. (See Figure IV – Predicted Origin of Feather Samples at Zones 95% Confidence on page 14) Figure IV – Predicted Origin of Feather Samples at Zones 95% Confidence Source: Bowen et al., 2005, p. 347 Measuring the stable isotopic ratios can guide the forensic scientists in terms of identifying and determining where the food sources came from. In some cases, analyzing the ratio of stable isotopes can make forensic scientists determine not only the movement but also diet and the origin of a person or an animal (Chesson et al., 2008; Bowen, Wassenaar and Hobson, 2005). Basically, all these are possible due to the fact that environmental factors such as “continentality” and “temperature” can significantly affect isotope ratios (Kreuzer-Martin and Jarman, 2007; Kendall and Coplen, 2001). As a universal knowledge, water is composed of elements such as hydrogen and oxygen (H2O). For this reason, it is common for forensic scientists to measure the stable isotopic ratios of hydrogen and oxygen when it comes to addressing the need to trace back the main source of water (BioZine, 2013; Lennard, 2012; Bowen et al., 2005). Stable isotopic elements such as carbon and nitrogen are present in food sources. For this reason, it is common for forensic scientists to trace back the main source of food stuff by measuring the stable isotopic ratios of carbon and nitrogen (BioZine, 2013; Lennard, 2012). Since each type of food has its own stable isotopic fingerprint, measuring the stable isotopic ratios in foods will enable the forensic scientists know whether or not the food stuff has been contaminated or not (BioZine, 2013). On top of being able to determine the origin of food and water sources, the process of comparing or matching the stable isotopic ratio with the victim’s DNA finger prints can help solve accident or criminal-related cases (Lennard, 2012). Stable isotopic profiling will also help forensic scientists determine the place of origin or residence of a person, evaluate the chemical composition of paints found in the crime scene, test the chemical composition of adhesive tapes used in a crime scene, determine the close link between the organisms and the environment where organisms grow, identify the country of origin of the dead body, determine the geographical history of a person particularly in the case of a terrorist, human tracker, or smuggler, and for forensic identification purposes, identify the history of illegal drug use, identify or detect the presence of counterfeited drugs, and when there is a need to solve arson cases. Likewise, forensic scientists are able to identify and convict people who are responsible for a crime just by going through the process of characterizing the microbial agents. This report is educational not only on the part of the students who are currently taking forensic science but also those who are studying chemistry. Using the information presented in this report, intended readers will be able to gain better understanding of the use and importance of stable isotopes in the study of forensic science. Since the scope of application or the usage of stable isotopes analysis in the study of forensic science is very wide, the study of forensic science was purposely divided into different forensic categories known as: (1) food forensics; (2) environmental forensics; and (3) wildlife forensics (Lennard, 2012; Philip and Monaco, 2012; Slater, 2010; Ehleringer et al., 2008; Bowen, Wassenaar and Hobson, 2005). Chapter 5 – Conclusion The universal application of radioactive isotopes in the study of forensic science is much limited as compared to the use of stable isotopes. This is true because of the fact that radioactive isotopes are chemically active. In the process of mishandling the radioactive isotopes, the lives of the forensic scientists can be endangered. Among the reasons why stable isotopes are commonly used in the field of forensic science lies behind the fact that isotopes are safe to use. Aside from its safety issues, stable isotopes can be easily found anywhere we go. For this reason, measuring the ratios of stable isotopes is more feasible as compared to the process of measuring the isotopic ratios of radioactive isotopes. To sum it all up, in the absence of physical evidences or in cases wherein DNA or fingerprint testing is not available, the use of stable isotopic ratios can play a significant role when it comes to solving criminal cases. All these are possible without the need to put the lives of our forensic scientists at risks. References Benson, S., Lennard, C., Maynard, P. and Roux, C. (2006). Forensic applications of isotope ratio mass spectrometry—A review. Forensic Science International, 157(1), pp. 1-22. 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