Introduction and Scope of Forensic Toxicology
Forensic toxicology is the study of all elements of toxins that have legal repercussions. In law enforcement, it has resulted in a significant decline in the number of chemical- and drug-related deaths and accidents. Forensic toxicology is applied in postmortem drug testing, workplace drug testing, and investigation of illegal materials (Becker, 2009).
Postmortem drug testing involves the investigation of death to establish whether the cause of death or one of the contributing factors of the death was drugs (Saferstein, 2006). Fatalities as a result of unintentional or premeditated drug overdose are many. On the other hand, there are some cases of death that are homicidal in nature. Forensic toxicology helps in establishing the nature of drug-related death.
The second application of forensic toxicology is in the workplace drug testing. This involves the assessment of biofluids from workers and candidates for drug content. The law normally permits unscheduled drug testing for workers in specific occupations such as security agents. In such occupations, the law puts the public security above the privacy rights of the employees concerned. Such employees may also be required to provide specimens to be tested for drugs if they seem to be weakened by the consequences of alcohol or other illegal drugs.
The majority of the employees do not go through mandatory forensic toxicology testing. However, job applicants are often mandated to go through drug testing as a pre-requisite for employment. The logic behind the drug-free employment condition is based on research studies which have shown that individuals who use illicit drugs are usually unreliable and unproductive at work (Becker, 2009).
The evaluation of contraband materials is the third application of forensic toxicology. As part of the nation-wide effort to halt drug abuse, laboratory support is needed by police agencies to establish that a confiscated material is indeed a forbidden material. For instance, if cocaine is found in the possession of a suspect, a conviction for illegal possession necessitates that the material be scientifically proven to be actually cocaine.
Such specifications are established by police agencies in the field using rapid, transportable testing kits. The success of forensic toxicology depends to a large extent on the forensic toxicologist who plays significant roles not only in the analysis of specimens but also in interpretation of the results (Becker, 2009).
The Role of the Forensic Toxicologist
The major role of the forensic pathologist is to elaborate the cause of each death that is under his or her jurisdiction and to establish the nature of the death, that is, if it was unintentional, suicidal or homicidal (Levinson, 2002). The forensic toxicologist immeasurably assists the forensic pathologist in carrying out comprehensive analyses of a wide range of toxins. Other roles of the forensic toxicologist include the identification, analysis and study of the effects of drugs, poisonous, and environmental chemicals on the human body.
Usually, toxicologists are mandated to establish the existence of unanticipated chemical substances in body fluids or tissues and to establish the amounts of that substance in the sample. Toxicologists are especially important in dealing with driving under the influence (DUI) incidents as well as other civil and criminal cases that involve the ingestion of toxic substances (Lee & Harris, 2006). The significant decline in the number of poisoning incidents over the last one and half centuries has been attributed to the ability of the forensic investigators to establish poisons in corpses.
Specimen Collection in Forensic Toxicology
Blood
Blood is the most crucial biofluid in forensic toxicology involving cadavers. This is because chemicals found in blood have a higher probability of having positive correlations with the lethal outcome as compared to other biofluids. Two blood samples are usually collected, one from the heart and the other from a peripheral location. The approximate volume of blood collected ranges from 50 to 100 milliliters (Goldfrank & Flomenbaum, 2006).
Urine
In work-related drug assessment, urine has better outcomes than blood because the former can be collected in larger volumes. In addition, urine collection process does not involve any puncture of veins. One possible disadvantage of urine is that the relationship between the amount of drug in urine and the drug outcome is normally weak.
Nevertheless, the rationale behind pre-employment screening is merely to establish if the individual has been actively engaged in consumption of illicit drug and urine is adequate in addressing this question. Urine is also used investigations of cadavers because some chemicals found in urine are in higher amounts than they could be in blood. The test of blood alone could therefore lead to negative results.
Gastric contents
The evaluation of gastric contents is advantageous in cases where a person died suddenly and was found to have large amounts of toxic substances in the stomach. If the person died by suicide, the presence of large amounts of toxins in the stomach may make it clearer (Goldfrank & Flomenbaum, 2006).
Vitreous humor
Vitreous humor is collected after a person dies. It is found in the eye which does not decay because it is a peripheral organ. The evaluation of the vitreous humor may be beneficial in ascertaining the time of death.
Bile and liver
Liver is the organ that is heavily involved in drug metabolism. It is probable to have huge amounts of a majority of the drugs and may occasionally allow the identification of a substance that led to death even if the substance is not present in blood. Bile drains from the liver and contains rich amounts of some types of drugs such as opiates (Goldfrank & Flomenbaum, 2006).
Analysis of Toxicology Specimens
The evaluation of organ tissue and biological fluids is hampered by the reaction of chemicals that takes place as cadavers decompose. As a result, it is usually recommended that the autopsy and testing of specimens be carried out immediately a person dies (James & Nordby, 2005). Forensic toxicology is usually carried out through a number of tests such as immunoassay test and gas chromatography-mass spectrometry (GC-MS). This latter test makes use of the difference in chemical characteristics between different parts of a mixture to separate the molecules (James & Nordby, 2005).
The molecules have different retention times of getting out of the gas chromatography, and every compound separated through this manner enters the mass spectrometer. The mass spectrometer then divides each molecule into charged portions in accordance with their mass. The GC-MS then makes a comparison between the spectra produced during analysis and its stored database until a match is found (Girard, 2008).
Gas chromatography has been used successfully in solving deaths that seemed a mystery to forensic scientists. For instance, one case involved a drug-facilitated sexual assault of a 13-year-old girl. Initial investigations failed to solve the mystery because no visible signs of physical harm, strangulation, rape or violence were seen.
Using GC, however, the forensic toxicologist found that the young victim had been sexually assaulted using chloroform whose concentration in the blood was found to be 833.9 mg/l. The outcome of this case inspired the need to search for poisonous substances in such seemingly mysterious cases (Gaillard, Masson-Seyer, Giroud, Roussot & Prevosto, 2006).
Interpretation of Toxicological Information
After the analysis, the forensic toxicologist assembles the findings, studies them, and then determines the actual factor that led to the death. The inference made from the data analysis is the most challenging work of toxicologists. They must establish the manner in which the drug was ingested, the quantity of the administered drug, and whether the administered drug was enough to lead to the death of the person. To establish the route of the poison administration, the toxicologist makes a comparison of the amounts of drug present in the specimens.
In general, the highest amount of poison will be found at the point of entrance into the body. If this concentration is found in the gastro-intestinal tract or the liver, it implies that the poison was administered orally. Illicit drugs such as cocaine, heroin and phencyclidine are usually taken through smoking. If the highest concentration of such drugs is found in the lungs than in other body organs, it implies that they were inhaled. For drugs that were administered intravenously, the highest concentration would be found close to the place where the drug was injected (Goldfrank & Flomenbaum, 2006).
In making interpretation of findings, the toxicologist must take caution of the possibility of administration of medical treatment such as blood and plasma transfusions just before the death. This is because such treatments may dilute or flush out poisons. The finding of poison in any body organ does not necessarily mean that it was the cause of death.
To establish its lethal impact, the toxicologist must conduct an analysis of other specimens to confirm that the poison was indeed absorbed and then transported to other body organs (Girard, 2008). Poisoning from very strong acids is however exempted from this rule. This is because strong acids such as sulfuric acid destroy tissues on contact and lead to severe bleeding and shock.
Alcohol and the Law
Laws against “drinking and driving” have been in existence since the 1800s. Nevertheless, drinking under the influence of alcohol became a public issue in 1933-1934. Indiana became the first state in 1939 to pass a “drunk driver” law. Blood alcohol concentration was used to determine the sobriety of a person. The “drinking and driving” issue has attracted the attention of many scholars who have been interested in showing how alcohol affects the skills needed for navigating a car, for instance, clear vision and balanced hand-eye coordination (Saferstein, 2006).
Alcohol metabolism
Alcohol passes from the mouth to the small intestine through the esophagus and the stomach. As it travels, it is absorbed into the bloodstream mainly from the stomach and the small intestine (Wurst et al., 2006). This absorption generates the blood alcohol concentration. Once it reaches the bloodstream, the alcohol is transported to the brain where the concentration of alcohol is equal to the BAC.
The rate at which alcohol is absorbed into the bloodstream is affected by many factors such as “the rate of gastric emptying, the presence of food in the stomach, the concentration of the ethyl alcohol taken in, the type of alcohol-containing beverage and the rate at which the alcohol is ingested” (Girard, 2008, p. 313).
Even though alcohol enters the body through absorption, the process is slow and takes a long time to distribute the alcohol throughout the body. Rapid distribution of alcohol is facilitated as the ethyl alcohol traverses into the internal membranes of the cells in addition to water. Water hastens the distribution of alcohol throughout the body’s tissues. As a result, the amount of ethyl alcohol in a tissue is directly proportional to the water content found in that tissue (Fracasso, Brinkmann, Beike & Pfeiffer, 2008).
Testing for alcohol
Law enforcement officers test for alcohol among drivers using various testing instruments the most common of which is the Breathalyzer. The Breathalyzer measures the concentration of alcohol in the suspect’s breath indirectly by measuring the absorption of light by potassium dichromate prior to and after reacting with alcohol (Saferstein, 2006). As the potassium dichromate continues to react with alcohol in the Breathalyzer, the amount of the potassium dichromate falls in the suspect’s sample.
On the other hand, the amount of light absorbed by potassium dichromate falls proportionally to the level of alcohol in the sample. The comparison between the sample of the suspect and the reference one leads to an electric current that forces the needle of the Breathalyzer to move from its initial resting place. The operator then moves the needle back to its resting place and reads the amount of alcohol recorded.
One major disadvantage of the Breathalyzer is that it consumes chemicals. Therefore, the test administering officer should continuously supply the Breathalyzer with adequate quantities of fresh chemical reagents. Failure to take this precaution may make the evidence inadmissible in court because defense lawyers may argue that the readings were false due to the use of outdated chemicals (Girard, 2008).
Besides the use of testing kits, alcohol consumption can also be tested through the analysis of blood using the gas chromatography method. The disadvantage of using this method on living beings is the need to draw a blood sample from them. The method can also be used to test for alcohol content on corpses. The process of blood collection from a suspect first begins by disinfecting the skin with a non-alcoholic disinfectant, for instance, Betadine.
This prevents the suspect from alleging that a high BAC level was influenced by the disinfectant. The collected blood sample is then kept in a refrigerator in an airtight container. Lack of refrigeration may render the BAC level to be abnormally low, whereas the failure of properly preserving the blood sample may render the reported BAC to be abnormally high (Girard, 2008).
In sum, forensic toxicology is an important field. It helps in solving so many criminal and civil cases which would otherwise seem a puzzle to the law enforcement authorities. Although widely used in alcohol-related incidents, other substances such as illicit drugs and poisons are also identified effectively using forensic toxicology. Despite its great potential in identification of chemical substances, care must be taken during the interpretation of findings because of the existence of many possibilities of the cause of death. Nonetheless, forensic toxicology has had profound effects in solving chemical-related cases which have in turn minimized the occurrence of such incidents.
Reference
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Gaillard, Y., Masson-Seyer, M., Giroud, M., Roussot, J., & Prevosto, J. (2006). A case of drug-facilitated sexual assault leading to death by chloroform poisoning. International Journal of Legal Medicine, 120, 241-245.
Girard, J. (2008). Criminalistics: Forensic Science and crime. Sudbury, MA: Jones and Bartlett Publishers.
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Levinson, D. (2002). Encyclopedia of crime and punishment, volume 1. Thousand Oaks, CA: SAGE Publications.
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