Forensic Toxicology: Poisons, Drugs, Scientific Analysis, and the Law

This is a paper I had to write for class, but it was rather an enjoyable project. I am very interested in this specialty, and it's interesting to delve into the cases, methods, and implications of this field. If you catch a typo or find yourself confused, leave a comment. I'm turning this in tomorrow, so last-minute corrections are possible. 

Toxicology is the study of poisons and poisoning. Baldly put, it seems a simple science, but the reality is far more complex, difficult, and encompassing than most people think it is. Application of the law to the science in the field only adds to the complexity of the study, as the stringent requirements of proof in court mean that the methods used must be of the highest accuracy and precision. Forensic toxicology, then, “uses the principles of analytical chemistry to identify potentially causative agent and toxicology to offer mechanistic reasons for impairment, illness, or death with the distinct applicability of these science to matters of the law.” (Middleberg, 2014)

Within forensic toxicology, then, we can find further divisions of the science. Human Performance Toxicology, which identifies and assess substances that can impair a person’s ability to perform. Alcohol testing would fall into this category, or the use of human growth hormone to enhance an athlete’s ability to perform in a contest. It could also include prescription drugs that cause drowsiness, or illegal drugs that cause retrograde amnesia and open the person to sexual assault.

Postmortem toxicology is more specific to poisons or drugs that lead to death, and can involve testing of the stomach contents, tissues, brain, hair, and fingernails to determine the substance, how long it had been present in the body, and the route it followed when metabolizing, which could have influenced the cause of death. Once the substances are known, they can be evaluated for their effect on the human body and determination can be made of their being the cause of death, and thus, the manner of death may be determined along with other evidence.

While not a major crime, as poisoning that lead to death or injury would be, Workplace testing is still an important facet of forensic toxicology. Screening the urine or blood of applicants and workers for illicit substances allows employers to be certain that they and the general public will be safe from those who are under the influence of some substance that would impair their ability to perform a task, such as operating heavy machinery.

Finally, there is the court-ordered testing of some individuals who were previously convicted of being under the influence, to ensure that they do not relapse into the use of drugs or alcohol while they are on probation or parole and still under the purview of the court. This application is, again, not linked to major crimes but is still an important tool in the prevention of recidivism, and viewed coldly, a savings of the State’s money in keeping repeat offenders out of prison, even without the human element of withdrawing an addict from a potentially fatal and certainly harmful substance they seek.

It seems ironic that historical knowledge of poisons and their effects was facilitated by a careful researcher who took copious notes on the “rapidity of toxic response (onset of action), the effectiveness of the compound (potency), the degree of response of the parts of the body (specificity and site of action), and the complaints of the victim (clinical signs and symptoms)” and who was herself a serial poisoner and would be prosecuted to the fullest extent of the law in modern times (Klaasen, 2010). Catherine de Medici was probably not solely the reason that women were considered first when poisoning was suspected, but she certainly reinforced that stereotype. Her work may have influenced Paracelsus, later in the Renaissance period, whose famous quote was “all substances are poisons: there is none that is not a poison. The right dose differentiates a poison from a remedy.”

From the birth of modern toxicology, and a scientific approach based on the study of the adverse effects of chemicals on the human organism, which included understanding the chemical, biochemical, and molecular mechanisms of action, forensic toxicology came into being. As a hybrid of analytical chemistry and ‘fundamental toxicologic principles that focus primarily on the medicolegal aspects of the harmful effects of chemicals on humans and animals” forensic toxicology demands a background in chemistry, biology, and the law. (Klaasen, 2010) In the past, there was no standard for forensic toxicologist, but in 2009, the Scientific Working Group in Toxicology (SWGTOX) was established with the goal being to set guidelines and eventually accreditation of scientists who work in the field. Since its inception the SWGTOX has set standards of method validation, testing, research, evaluation, and a code of conduct.

To become a clinical toxicologist, a candidate should have a PhD in a chemical, physical, or biological science, and be certified by a board.(SNA International, 2016) However, a forensic toxicologist who will be working in a laboratory rather than directly with diagnoses of poisonings, can have a masters in a physical science with some experience working in a forensic science laboratory, or can have a BS in physical science with extensive experience working in a forensic science lab. (Career Portal, 2016) To gain this experience, the person who is interested in attaining the status of forensic toxicologist would begin work at a forensic laboratory where they would have opportunities to become familiar with the types of instrumentation and tests they would perform later on.

A forensic toxicologist uses many tools to perform the analyses of substances. Toxic substances may be classified into several categories by their origin or nature: gases, volatile substances, corrosive agents, metals, anions and nonmetals, nonvolatile organic substances, and miscellaneous. Classification of a substance helps determine the method for separation of a toxic substance from the matrix in which it is embedded, such as a protein or other cellular component. They can expect to perform at least two different techniques on given samples from a case, with two different principles if possible, and one of those being molecular identification through some method (Middleberg, 2014). For organic substances, this would most likely be either gas chromatography-mass spectrometry, or the currently more accepted liquid chromatography-mass spectrometry. Immunoassay (ELISA) techniques are sometimes used, but have a lower degree of confidence in their accuracy. TLC, thin-layer chromatography, is infrequently used.

Laser Diode Thermal Desorption – Tandem Mass Spectrometry (LDTD-MS-MS) is one of the new technologies being evaluated for use in forensic toxicology. The accuracy for results in urine ranges from 88.9 to 104.5% and in blood from 91.9 to 107.1%, and the advantages of the system are the minimal maintenance and rapid analysis (about 10 s per sample) but the disadvantage is the difficulty in detecting isomers due to the lack of chromatography. Use of this tool in rapidly screening would help decrease the time needed to run samples through the longer analysis time of the chromatography-based methods. In this method, a typical 2µL sample is pipetted into a well, and when the solvent evaporates, an infrared laser diode vaporizes it. The analyte is carried along with a neutral gas into a corona discharge to ionize the analyte. The mass spectrometer then reads detects the ions and compares them to the database of known specimens. (Bynum, 2014)

A brief overview of the primary analytic methods used to detect, analyze, and determine amounts of substances in a given sample will focus primarily on gas or liquid chromatography, and mass spectrometry. Chromatography is a method of separation using two phases, a mobile phase and a liquid phase. Gas chromatography is suitable only for volatile and thermo fragile molecule, liquid chromatography is able to separate non-volatile and thermo labile molecules. (Gahlaut, 2013) Detectors for the eluent of chromatography can include refractive index, electrochemical, fluorescence, and UV-Vis spectrometers, but the most used in toxicology will be the mass spectrometer . Once the eluent leaves the chromatography tube (either LC or GC) the mass spectrometer ionizes it, and then generate the mass spectrum based on the fragmented ions mass to charge ratio (m/z). This spectrum is then compared by the computer to a vast database of known substances for an accurate identification of the unknown substance.

Preparation of the sample, filtration, extraction of biological or chemical elements, the standards used for comparison or the database compared against, all these factors must be carefully recorded as they will be invaluable in the courtroom. However, even before the sample arrives in the lab, a careful record of the collection of the samples must be kept, as the improper care and handling of specimens can defeat the purpose of the tests, and can negate the evidentiary benefit of the testing if the samples can be shown to have degraded before testing. During testing the analyst will maintain chain of custody, keeping logs of what samples where handled, when, and by whom. Forensic toxicology analysts should always remain acutely aware of their safety while handling specimens, keeping in mind that infectious disease can be carried by most if not all the samples presented to them. (Dinis-Oliviera, 2010)

Consideration must be made of the samples which were collected post-mortem, as the body is not static after death, and the changes in the tissues as they begin to break down immediately following death also affects the substances found within those tissues. For instance, a basic substance, pKa >7, will be more widely redistributed after death, as they were usually more concentrated in the tissues before death (relative to acidic substances) and the tendency of a cell to become more acidic after death, resulting in the basic substance being more aggressively ionized (Dinis-Oliviera, 2010)

Once the samples have been collected, time is of the essence in analysis. Some drugs and poisons have a very short half-life, and must be tested as soon as possible before traces of their presence are gone. Benzodiazepines (a class of psychoactive drugs) are subject to post-mortem changes and unless held at -60ºC, will be unstable and break down. (Dinis-Oliviera, 2010). Heroin decomposes through the actions of enzymes in the blood plasma in only a few moments in a living subject, leaving only the metabolite 6-acetylmorphine behind to be tested for. Understanding these changes in many substance as they react in the body either before or after death is essential to the ability to test for their residues and metabolites.

Samples presented to the forensic toxicologist may not always be directly from the human subject. Insects feeding on the body after death are known to ingest substances in the tissues, and analysis of the insects can be helpful in identifying the substance and the quantity at which it was present in the host body. Regardless of where the sample came from, the forensic toxicologist should be prepared to face a battery of questions about the analysis, methods used to conduct that analysis, and their interpretation of the results. These questions will come from legal, law enforcement, and medical personnel associated with the case, and the analyst must be prepared for provision of accurate and concise answers in plain English as they speak outside their field to lawyers and the jury who need to fully understand the analysis.

Case Study 1:

In 2008, a tragic case was investigated in Nivaana village, District Jaipur, India. Initially suicide was suspected in the deaths of a man, his wife, and their two young sons. Only through the diligence of the investigators and their willingness to look deeper into the evidence was the initial ruling of death by suicide overturned. At the crime scene, the four persons were discovered dead in their homes, and as the scene was processed, special note was taken of liquid in some pots, and the number of medicines found in the home. One of the pots was noted to have the smell of an insecticide the investigators were familiar with, but there was no vomit at the scene. No containers of the insecticide were found at the house. The amount of medicines found in the house indicated to the investigators that someone in the house worked in the medical field.

It became obvious to the investigators that because there were cleaned pots and pans, and there was no container of poison to be found, this was not a case of suicide. Instead, they began to treat it as a murder. However, there were no signs of a struggle from the family being subdued and poisoned, and the house had not been ransacked for loot.

The investigators had testing done on the blood and tissues of the deceased, but the methodology is not listed, only the results of the discovery of Endosulfan, Penatocine, Phenargan, and Ketamine. The Endofsulfan was also detected in urine, food, and a syringe. Another syringe contained ketamine, and it was determined that these chemicals, administered intravenously, had been the cause of death. The hypothesis of the investigators thus proceeded from suicide, to homicide via oral ingestion of a poison, to injection of a poison, and the crime scene corroborated the toxicology reports. Thus, the investigators were searching for someone close to the family with medical training who would be trusted to administer an injection to them. The eldest son was determined to have the drugs necessary, the training, and the motivation of being able to sell his parent’s house for money. When confronted, he confessed to the murder which he had carried out after long planning. (Sharma, 2010)

Case Study 2:

In this case of murders and a suicide, there was little doubt of the cause of death, but still procedures were followed to confirm the story the scene told to the initial investigators who arrived to face a tragedy. Alerted by the neighbors, police entered the house to discover three dead children, and in an adjacent barn, the body of their father, who was hanged. On the table near the children was a bottle labeled as chloroform. The father had left a letter stating that he had first given them sleeping pills, then used the chloroform on them, and finally suffocated them with plastic bags once they were unconscious.

In the lab, doxylamine (an antihistamine also used for a sedative) in therapeutic concentrations was found in the blood and urine of the children. Analysis of the blood and urine was performed with GC-MS for chloroform. The urine tested negative in all three subjects, and the blood showed varying levels. Interpretation of those results, with the concentration of chloroform in the blood being 73, 5, and 102 mg/L respectively, indicates that as death is known to occur at an average concentration of 64 mg/L, two of the children died of their overdose of chloroform, and the other would have been killed by anoxia as a result of suffocation. (Ribe, 2001)

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