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While the technology available to the forensic toxicologist is far superior to that of 170 years ago, the analytical challenges remain the same. And while the understanding of pharmaco/toxicokinetics and dynamics has advanced, the questions remain the same.
It could be the year 1850, or 1950, or 2008…take your pick. It was a few days since the family dinner that the husband took ill. The nausea, vomiting, and diarrhea had been relentless. And that garlic taste in his mouth, it just wouldn’t go away. And finally, almost as a relief, he died. Whether as a relatively new bio-analytical science in 1850, or a discipline with remarkable, state-of-the-art equipment today, forensic toxicology has been asked to address concerns with such cases, to speak for the victimized husband, to tell the story of what caused his illness and death, and to provide the “smoking gun,” the identification of the arsenic that led to the wife’s conviction. Truth be told, however, things are neverso clear. What follows is an accounting of the past, present, and “future” states of forensic toxicology, a discipline key to a wide variety of case types ranging from pre-employment testing to death investigation.
THE DUALITY OF FORENSIC TOXICOLOGY
Forensic toxicology is a scientific discipline with a split personality. While toxicology can be defined as the study of the adverse effects of chemicals on living things, the forensic component also mandates an analytical component. In this latter regard, the forensic toxicologist is also an analyst, or more to the point, an analytical chemist. It is the ability to bridge the two fields that defines the proficiency of any forensic toxicologist. The application of the two fields to cases ranging from: human performance issues, e.g., driving under the influence of alcohol and drugs; workplace testing and athletics; clinical toxicology, e.g., helping to diagnose the poisoned patient; and, postmortem issues, e.g., helping to determine a cause of death, all make this field dynamic and fascinating. However, understanding the modern development of this duality sheds light on the impact of forensic toxicology on our criminal and civil justice systems and society.
The origin of modern analytical toxicology, and for that matter forensic toxicology, is often attributed to a Spanish physician named M.J.B. Orfila who actually practiced his vocation in France during the early to mid-1800s. Despite the establishment of laws against poisoning dating back to 81 B.C.E., it was his analysis of autopsy materials to identify poisons, and the subsequent accounting of such, that represented the first systematic approach to the identification of poisons. It was this approach that led to the first courtroom toxicological testimony by Orfila in 1840 during the trial of Marie Lafarge in France for poisoning her husband to death with arsenic.1-3
If one focuses solely on arsenic, the evolution of bio-analytical forensic toxicology is easily made clear. Even prior to Orfila, a number of chemists worked on the identification of this widely used poison during that time period. Most of the developed tests surrounded the precipitation of arsenic through oxidative and reductive processes. Unfortunately, none of these tests proved sensitive enough for forensic toxicological purposes. However, in 1836, James Marsh, a British chemist, published an improved, sensitive method for the detection of arsenic. This method allowed for the physical presentation of the arsenic finding in a courtroom, and in fact, was the test used by Orfila in the Lafarge case.4 In 1842, Hugo Reinsch developed the namesake test that “plates” arsenic onto copper wire, turning it black. This was followed by Max Gutzheit’s semiquantitative test in 1879, again ultimately involving precipitation of arsenic. This latter test remained a hallmark in arsenic testing for almost 100 years.5 In the mid-1950s, Alan Walsh developed atomic absorption spectrometry. Within a decade or so after that, this instrumental technique was being readily used for a variety of elemental analyses, including arsenic. In the mid-1980s, ICP-MS (inductively coupled plasma-mass spectrometry) was made routinely available, a method recognized as the current standard in arsenic testing.
In summary, for approximately 140 years, arsenic analysis was via precipitation or plating techniques, and then over the next 40 years, instrumental techniques became the norm, thus providing better selectivity and sensitivity. This sort of history of arsenic testing can be applied to almost all substances of toxicological interest. Early techniques were qualitative in nature and as instrumental methods took hold in the 1950s, analytical methods that offered substantial improvements in selectivity and sensitivity became of practical and facile availability to the forensic toxicologist. Today, the field is dominated by instrumental methods, especially mass spectrometric techniques, e.g., GC-MS (gas chromatography-mass spectrometry), LC-MS (liquid chromatrography-mass spectrometry), related tandem mass spectrometric techniques (GC-MS/MS; LC-MS/MS) and ICP-MS. But, for the budding forensic toxicologist, some of the older techniques should not be dismissed since they still remain viable and of significant value. This is especially true since the mantra of forensic toxicological testing remains—whenever possible, confirm the presence of a substance using two techniques that utilize two different physico- chemical processes.6
What the future holds for bio-analytical toxicology is anyone’s guess. If history holds true, and since mass spectrometric and other techniques are still maturing, it may be a little while before the next major fundamental analytical breakthroughs occur. However, that does not mean that major improvements may take place. By far, for the field, substantial advances in sample preparation techniques are in dire need. These processes, which isolate substances of toxicological interest from various matrices, e.g., blood, urine, tissues, etc., in many ways, are still, in principle, those used over 100 yearsago. Advances in speed, decreased solvent usage, and specificity are all needed and would be welcome within the forensic toxicological community.
Toxicology is a biomedical science. The three main areas of toxicology—descriptive, mechanistic, and regulatory toxicology all advance our knowledge of basic biochemical and physiological processes, health and safety, and risk assessment. The descriptive branch of toxicology involves, as its name implies, the description of some phenomenon related to toxicology, whereas the mechanistic area attempts to determine what is at the root of the toxicological process, generally at the macro- and microlevels. The regulatory discipline applies the data from the descriptive and mechanistic arenas to develop various risk assessments for the sake of public safety. Forensic toxicology is considered a specialty field within toxicology.1
Basic sub-disciplines within pharmacology and toxicology employed daily by the forensic toxicologist include pharmaco/toxicokinetics and pharmaco/toxicodynamics. Simply put, the former is what the body does to a drug or chemical, whereas the latter is what the drug or chemical does to the body.
Included in pharmaco/toxicokinetics is what is monikered, ADME, aka, Absorption, Distribution, Metabolism, and Elimination. These actions represent what the body can do to a drug or chemical once exposure has taken place. Pharmco/toxicodynamics describes drug or chemical actions that occur in the body once exposure takes place, and such actions range from no observable effect to death, and everything in-between. Descriptions of both processes can be found as far back as 1500 B.C.E. in the Smith and Ebers Papyrus.7 While most of the early toxicological writings were descriptive in nature, in the early to mid-1500s, toxicological assessment took a turn toward the modern practice of this science. In this time period, a Swiss physician named Paracelsus developed relevant corollaries and such regarding toxicology through experimental and observational processes. He coined the driving motto of all toxicologists, that is, “The dose makes the poison.” In a modern sense, this term can be construed as meaning “enough of anything can be toxic.”8
In particular respect to forensic toxicology, the crux of the matter is always, “What do a set of analytical toxicological findings mean?” By applying the principles of kinetics and dynamics, the forensic toxicologist can attempt to answer this question to varying degrees. The answer to this, and other questions of forensic toxicological interest, cannot usually be based solely on analytical findings, however. It is the holistic nature of a case that allows for interpretation, with the accent on holistic. The more information that is available about a case or individual, the better the chance a forensic toxicologist can provide assistance. However, even when armed with knowledge about the case or individual, this does not guarantee forensic toxicological assistance in any given case. In contrast to the analytical component of this field, with today’s advancements in knowledge in toxicology, there is also often less clarity around the interpretation of findings. Today, the forensic toxicologist has to consider several ante- and postmortem phenomena, e.g., postmortem, or site-dependent, redistribution of substances after death, whereby drugs and chemicals can “move” from one site to another within the body after death; drug or chemical interactions, a phenomenon where one substancecan interfere with the metabolism and elimination of another substance, thus leading to accumulation of the latter compound, and an increased risk of toxicity; pharmaco/toxicogenomics, where the same enzyme in the body responsible for metabolizinga particular compound may function too well or too poorly in any given person;etc. All of these, and other factors, sometimes make toxicological interpretation difficult, perilous, or impossible.
Undoubtedly, the future may provide greater and greater toxicological information, but it is not a certainty that this will add interpretive clarity for the forensic toxicologist. Pragmatically, since individual response, both kinetically and dynamically, will never be able to be fully accounted for, toxicological findings will always have some difference in interpretive value based on the practitioner.
SPECIFIC CHALLENGES IN FORENSIC TOXICOLOGY
Every generation of forensic toxicologist has had to endure numerous challenges outside of those already expressed. Many of the cross-generational challenges are similar with the details being the only differentiating factors. In this respect, the following are but a few of the major, day-to-day specific challenges on top of those previously described. First and foremost is being qualified to be a forensic toxicologist. The dual nature of the field make this particular challenge a long and arduous journey, certainly not meant for individuals seeking instant gratification. While there are many ways to become a practicing forensic toxicologist, there seems to be some basic commonality amongst such professionals. That is, basic educational requirements consisting of some combination of analytical chemistry and toxicology, often as separate educational endeavors, followed by mentoring and experience. Today, there are Board Certification programs for both the individual practitioner and the forensic toxicology laboratory. While offering no strict guarantees, appropriate certification generally demonstrates satisfactory compliance with the knowledge and principles necessary to function as both a forensic toxicologist and forensic toxicology laboratory.
As the challenges confronting the toxicological interpretation of findings have been previously discussed, a focus on the analytical challenges is also warranted. Forensic toxicologists don’t get a whole lot of say in the specimens they are asked to analyze, especially in the postmortem world. Specimens ranging from blood to urine to liver to brain to bone to hair all come with significant challenges based on the matrix composition. Add to that the state of the specimen, i.e., badly decomposed, covered with maggots, etc., and the challenges become even greater. While “tricks of the trade” are available to tackle such daunting specimens, sometimes such challenges cannot be overcome.
Further taxing the forensic toxicologist are the varied substances that may be of significance in any given case. Literally, forensic toxicologists must be able and capable to handle any of the forms of matter—solid, liquid, and gas. There are approximately 35 million or so chemical entities with registered names and probably multi-millions more in nature that have not been identified.9 Most cases in forensic toxicology, except for Federally-mandated workplace testing, are comprised of unknowns, i.e., anything may be present in any given specimen. While many of the 35 million or so compounds are not of toxicological concern, many others are of such concern. Faced with such a mountain of potential substances, the task, in the absence of additional information, can be daunting. While less than desirable, due to limitations in budget, staffing, and other pertinent factors, most forensic toxicology laboratories routinely screen for perhaps a few hundred to a few thousand compounds. When coupled with the drug culture, whose mission often seems to be to create new compounds either not controlled by governmental bodies or those that avoid current analytical schemes, and the herbal and diet supplement cornucopia, the ever growing number of compounds of potential toxicological interest is staggering. Meeting such analytical challenges is a difficult task at best and moving into the future, will only get more difficult.
The last significant challenge for the forensic toxicologist, like all forensic scientists, is the courtroom. It is a world that, no matter how long one has practiced, remains foreign. Unlike many other forensic disciplines, the analytical findings are not the sine qua non of the testimony. Most commonly, it is the opinion of the forensic toxicologist that is sought, the very thing that elicits the best in the adversarial nature of attorneys. Rarely are toxicological opinions certainties, but if done carefully and with Aristotle’s three appeals in mind, i.e., Ethos (ethical appeal), Pathos (emotional appeal), and Logos (rational appeal), the process can be intellectually rewarding.10 The toxicologist’s job is to teach the trier of fact something so a decision can be based on all available information; it is not the toxicologist’s job to be an advocate. Science by definition is truth-seeking, and forensic toxicology falls smack in the middle of that definition.
The car accident was horrific. A promising, community beloved, young coed, driving home on winter break, got broadsided by another car and killed. The suspect driver was taken into custody and a blood specimen was drawn. All that was found in the individual’s blood some two hours after the accident was benzoylecgonine, a pharmacologically inactive metabolite of cocaine. While under intense pressure, the State’s toxicologist testified that the suspect driver was impaired at the time of the accident. The defense attorney hired a forensic toxicologist who opined that there was no way to state with a reasonable degree of scientific certainty that the suspect driver was impaired at the time of the accident. The defendant was found not guilty of vehicular manslaughter while impaired and utter outrage was everywhere in the close knit community.
In the world of forensic toxicology, these scenarios play out almost every day. The same issues that burdened Orfila in 1840 continue today in 2008. While the technology available to the forensic toxicologist is far superior to that of 170 years ago, the analytical challenges remain the same. And while the understanding of pharmaco/toxicokinetics and dynamics has advanced, the questions remain the same. It is likely that 170 years from now, the same or unique other challenges will still exist. It is hoped, as toxicologists today have learned from the efforts of those before us, future forensic toxicologists will do the same. In this way, the field will get closer and closer to what can never be attained in most cases in terms of absolutes, but, as we do today, with stronger and stronger reasonable scientific certainty than those before us.
- Casarett & Doull’s Toxicology. The Basic Science of Poisons. C.D. Klassen (ed.). McGraw-Hill, New York (2001).
- Langman, L.J. and Kapur, B.M. Toxicology: Then and Now. Clin. Biochem., 39, pp. 498-510 (2006).
- Nemec, J. Highlights in Medicolegal Relations. National Library of Medicine
- Brindle, I.D. Vapour-generation Analytical Chemistry: from Marsh to Multimode Sample-introduction system. Anal. Bioanal. Chem., pp. 735-741 (2007).
- Forensic Toxicology Laboratory Guidelines (2006). SOFT/AAFS Laboratory Guidelines Committee.
- The Dose Makes the Poison. 2nd ed. M. Alice Ottoboni, Van Nostrand Reinhold, New York (1991).
Robert A. Middleberg, Ph.D., DABFT, DABCC-TC is V.P. of Quality Assurance, Laboratory Director, and a practicing Forensic Toxicologist at NMS Labs. Dr. Middleberg completed his doctoral studies in Pharmacology at Thomas Jefferson University and Medical College in Philadelphia in 1990. Previously, he was an analytical forensic chemist for theCommonwealth of Virginia’s Bureau of Forensic Sciences. Dr. Middlebergis a diplomate of the American Board of Forensic Toxicology and the AmericanBoard of Clinical Chemistry in Toxicological Chemistry and a member of severalscientific societies. He is on the Board of Directors for the American Boardof Forensic Toxicology and has served as Toxicology Section Chair for the AmericanAcademy of Forensic Sciences. He can be contacted at email@example.com.