Science of Forensic Toxicology Prior to Modern

Science of Forensic Toxicology

Prior to modern medicine and the advent of forensic toxicological sciences, death from intentional poisoning was often indistinguishable from natural causes.

Consequently, poisoning with toxic substances was a preferred form of murder throughout human history until relatively recently. Arsenic, in particular, was used so often as a method of murdering wealthy elderly relatives, that it was sometimes known as "inheritance powder."

Prior to the nineteenth century, it was virtually impossible to establish poisoning as the cause of death, even where it was strongly suspected, owing to the unavailability of any scientific means of conclusively identifying specific poisons in bodily tissues. By 1787, Johann Daniel Metzger demonstrated a method of identifying the presence of arsenic within food, but it was another two decades before method was first devised for identifying the poison within bodily organs and tissues.

Initially, it was the work of two scientists who improved these earliest attempts to establish the science of Toxicology. Mathieu Joseph Bonaventure Orfila published the Treatise of General Toxicology, in which he listed and classified all known toxic poisons. After demonstrating the ability to establish the tissue distribution of arsenic in animals, he became the first toxicologist to assist criminal investigators in suspected murder by poisoning.

At about the same time, James Marsh introduced an acid distillation method for illustrating the presence of arsenic, which became known as the Marsh Test. One of the significant advances of the Marsh Test is that it allowed criminal investigators to test soil for the presence of arsenic in order to eliminate ground contamination as a source of arsenic isolated in corpses exhumed in connection with homicide inquiries.

These preliminary advances in the growing science of forensic toxicology resulted in the first murder conviction in 1840 in England, and in the subsequent passage, in 1851, of the Arsenic Act, prohibiting the sale of products containing arsenic except to people over the age of twenty-one with proper identification and the inclusion of their names in a register maintained by chemical suppliers and merchants.

The next stage of development in the science of toxicology was also spearheaded by a student of Orfila, Jean Servois Stas, when he used ether as a solvent to isolate vegetable alkaloids from organic tissues, originally, in a case of murder by forced consumption of deadly quantities of nicotine. This particular advance eventually enabled toxicologists to identify many other deadly toxins capable of being used for murder such as morphine, strychnine, opium and quinine.

As the pharmaceutical and chemical industries grew, many more toxic substances became available to those who would use them for nefarious purposes.

These synthetic alkaloids required an entirely different method of identification, such as paper chromatography, based on separation of substances based on their respective molecular size and other chemical properties such as polarity, introduced in the middle of the twentieth century. The final conceptual and technological advance that marked the modern era of forensic toxicology was the subsequent development of gas chromatography and spectrometry, which enable the very precise identification of thousands of different toxic compounds and an accurate measurement of their exact concentrations within organic tissues.

The Modern Science of Forensic Toxicology:

Toxins are defined as substances (including solids, liquids, gases, organic and vegetable sources) that are capable of producing death by absorption through inhalation, ingestion, or through permeating the epidermal tissues. Modern scientists classify poisons as one distinct group of toxins that are either introduced into the body in a single massive dose or which saturate organic tissue in harmful levels, gradually.

Consequently, most poisons are readily detectable within the human body, owing to their high concentrations within tissues as well as the obvious medical symptoms associated with their effects.

Toxins, on the other hand, can be much more difficult to identify, because they are typically present only in comparatively minute quantities which usually produce more subtle medical symptoms capable of being confused with symptoms of known medical diseases. Generally, detection of toxic substances requires much more sensitive equipment, especially to establish exact levels of tissue concentrations.

Modern Toxicology consists of several distinct scientific specialties:

Descriptive Toxicology relates to the testing of potentially dangerous substances for the purpose of classifying their levels and types of risks to biological organisms,

Mechanistic Toxicologists investigate the mechanisms by which toxins affect organic tissues, and Regulatory Toxicologists synthesize the studies of toxins in order to determine the appropriate level of government regulation of specific substances.

Forensic Toxicologists examine blood and other fluids extracted from victims of crimes as well as organs and other viscera removed from cadavers. Sophisticated modern techniques combining gas chromatography and mass spectrometry allow forensic toxicologists to identify thousands of specific substances by comparing samples with their known, catalogued chemical and physical molecular properties.

In modern law enforcement, forensic toxicologists collaborate with forensic pathologists to determine the precise cause of death, or to exclude toxic contamination where cause of death results from some other mechanism. Technically, toxicologists may only offer testimony as to the characteristics of various toxins, or hypothetical arguments based on elements of cases where they are not witnesses to the specific case in question.

Law enforcement applications of forensic toxicology is instrumental in many different types of investigations, whether determining the precise cause of death, or the circumstances surrounding it where the actual cause of death is already known or otherwise obvious. Just as important is the ability of criminal investigators to eliminate poisons or other toxic substances as causes of death.

In criminal investigations not involving murder or other causes of human death, forensic toxicology is still crucial in the determination of both alcohol intoxication and illegal drug use or possession. Analyses of blood samples obtained after vehicular accidents and industrial catastrophes enable law enforcement and regulatory authorities to narrow their investigative focus in accordance with the factors actually responsible.

Established principles of forensic toxicology have also led to the development of field tests employed by drug recognition experts, as well as by ordinary police personnel for preliminary field testing of suspected controlled substances in the possession of subjects pursuant to on-the-spot criminal investigations or drug transportation interdiction, enabling the taking of appropriate enforcement action and substantiation of criminal charges.

Violent crime investigators rely on forensic toxicology to match suspects in rape and other sexual assaults by DNA sequencing of bodily fluids while absolutely excluding innocent suspects. Similarly, homicide investigators employ principles originally perfected by forensic toxicologists to test subjects for the microscopic presence of gun powder residue on their hands while eliminating those uninvolved.

Other modern law enforcement tactical tools that incorporate basic forensic toxicology principles include the breathalyzer, routinely used throughout this country and others) in conjunction with DUI enforcement efforts. The benefit of these tools is that they provide instant data for use in the field, where immediate thorough laboratory analysis is impractical if not altogether impossible. Where necessary, preliminary field results are subjected to more thorough, extensive testing for definitive confirmation of preliminary results obtained in the field.