Forensic Analysis in Toxicology
Forensic toxicology is a multi-disciplinary field combining toxicological principles,
analytical chemistry and methods, analytical toxicology, clinical chemistry, pathology,
pharmacology, investigative research, data collection and collation — and
a certain amount of detective work. TCAS has extensive expertise in forensic
toxicology with more than 34 years of conducting hands-on investigations.
Principles of Forensic Toxicology
The ultimate goal of forensic toxicology is to correctly establish or refute causation
to reasonable toxicological certainty. Aside from assessing each piece
of evidence on its own merits, the forensic toxicologist must rule out other possible
factors before drawing conclusions. Thus, the nature and steps of a forensic investigation
are primarily based on the circumstances and available facts pertaining to the case
itself. However, every case is different and there is no guarantee that there will
be sufficient toxicological evidence to provide a decisive opinion.
To produce scientifically credible reports and opinions, the expert forensic toxicologist must
conduct his investigation and assessment pragmatically. Evidential factors may include
medical records, symptoms, treatments, dosages, environmental conditions and events
(sometimes over a period of many years), historical records, laboratory data, etc.
In criminal investigations, crime scene evidence, police reports, witness statements,
autopsy reports, postmortem interval and analytical toxicology reports all contribute
to reconstructing events.
Although the forensic toxicologist goes where the evidence leads, he must be prepared
to factually recount on demand all of the investigative steps taken to derive the
reported results. This is a critical responsibility as a forensic investigation
may or may not lead to a determination of causation.
Forensic Toxicology in Litigation
Toxicological opinion(s) presented as expert testimony can significantly impact the
outcome of a case. Although the outcome of a forensic investigation is
relevant to the parties involved, proving or disproving a case is a matter for legal
counsel. The toxicologist can only offer opinions and evidence to assist and educate
the judge and the jury.
Thus, accurate compilation and objective interpretation of investigative results
are central to any responsible forensic toxicological assessment. When deposed and
questioned by counsel, the expert toxicologist must be keenly aware of the obligations
and responsibilities thus imposed:
- Case Knowledge: The toxicologist must be prepared
to testify regarding the basic facts of the case and answer questions pertaining
to circumstances. He may be questioned at great length on what might otherwise be
presumed to be trivial matters. Thus, the toxicologist's testimony will only be
regarded as credible if he possesses a working knowledge of case facts.
- Qualifications and Integrity: The toxicologist
must stay within his area(s) of expertise, deferring non-toxicological matters to
other experts and authorities.
- Foundation of Opinions: The toxicologist must
be able to clearly and concisely communicate the generally-accepted method(s) that
were used to conduct the investigation and/or arrive at opinions or conclusions.
This may include explanations of any relevant studies or citations applicable to
- Degree of Certainty: The toxicologist must define
the degree of certainty of his conclusions. Toxicological opinions should be expressed
as conclusions arrived at within reasonable toxicological certainty.
- Credibility: The toxicologist must expect that
opposing counsel will attempt to refute or discredit his testimony and may even
enter motions to exclude. In such instances, the toxicologist must be prepared to
produce objective rebuttals supported by generally-accepted methods and peer-reviewed
epidemiological studies and/or case evidence.
- Ethical Coherency: The toxicologist must be thorough
without being redundant and complete without transgressing into unrelated areas.
If confronted by difficult or misleading questions, he must respond with concise
professionalism, integrity and dignity.
As previously stated, the impact of a well-constructed toxicological assessment
in litigation can be instrumental in assisting the judge and jury in understanding
the case evidence. A scientifically credible report can provide key information
as to the contaminant(s) present in an individual as well as the dose of each substance
and whether the levels are consistent with a therapeutic dosage and/or adverse health
effects. When such results are presented as testimony with respect to a substance's
potential effect on an individual's death, illness, or mental or physical impairment,
these factors can have profound evidentiary impact. For example, the results of
a blood analysis from a driver involved in an automobile accident can be used to determine
if the individual was under the influence of drugs or alcohol.1
Similarly, the amount of a substance in the blood can be compared to levels documented
in generally-recognized, peer-reviewed studies to demonstrate or refute general
or specific causation.
Compliance with Scientific Methodologies
Because the forensic toxicologist goes where the evidence leads, it is critical
that the investigative procedure be based upon generally-accepted, peer-reviewed
methods. The forensic toxicologist may be confronted with a massive volume of evidence
which must be carefully analyzed, compiled and reduced to isolate relevant investigative
components. In other cases, little or no physical evidence may exist. Thus, there
are sometimes important investigative avenues to be explored. Although evidence
may ultimately appear, the forensic toxicologist must sometimes develop opinion(s)
from extrapolation of information. This may come from paper-based records, autopsy
records, physician reports, company memos, police reports, first-hand accounts (in
the form of sworn statements or deposition testimony), questionnaires, studies,
specialized analyses of blood, tissue and/or environmental samples — in other
words, every conceivable source of information.
To this end, it is extremely important to be thorough when assessing the available
data, particularly where data quality is concerned. For example, quality control
can be critically important for some substance measurements and the forensic toxicologist
should do more than merely accept summarized laboratory results. All available raw
laboratory data should be acquired and reviewed, particularly the actual GC/MS spectrometry
analyses for such methodological factors as (a) mass ion fit, (b) retention time,
(c) baseline noise and other analysis artifacts. Any or all of these data components can
prove to be relevant to the overall toxicological assessment.
Although forensic evidence varies as widely as the cases themselves, the requirements
imposed on the expert toxicologist are strict, particularly with respect to expert
testimony. There can be no "gray" areas if the toxicologist's testimony
is to be regarded as scientifically credible. In particular, there can be no "novel
methods" used to present opinions or conclusions. Credible testimony must be
presented in compliance with the Frye or federal Daubert standard:
"While courts will go a long way in admitting expert testimony deduced from
a well-recognized scientific principle or discovery, the thing from which the deduction
is made must be sufficiently established to have gained general acceptance in
the particular field in which it belongs."
Forensic Toxicology Archives
The following archive illustrates some of the methods and investigative techniques
TCAS employs to conduct forensic toxicological assessments. Toxic exposure
studies provide descriptive and instructional information pertaining to some of
the various toxic agents with which TCAS has been involved on numerous
occasions. Toxicology case studies are impartial and objective summaries of toxicological
matters in which TCAS was retained for the purpose of assessing health-based factors
which, in some cases, led to a determination of causation. No names or identifying
information have been provided due to privacy and legal considerations.
|TCAS has been involved in numerous cases involving TCDD exposures. We have had considerable experience in conducting toxicological risk assessments for TCDD, PCBs and other dioxin congeners. As part of our approach to presenting toxicological information in a manner that can be easily understood by a judge and jury, we have produced many demonstratives... (more)
|For more than two decades, TCAS has been retained in cases involving LNAPLs. We have significant experience in establishing the source(s), age and characteristics of LNAPL. We have performed LNAPL risk assessments on behalf of individuals, private industry and government agencies such as the New York State DEC, New Jersey DEC and others . We have offered unbiased... (more)
This case study illustrates how circumstantial evidence can be misinterpreted and how drug-impaired judgment and behavior can be regarded as evidential in a toxicological causation assessment. A motorcyclist was fatally injured when he collided with a city bus in a business district... (more)
|This case study summarizes the events leading up to and following a fatal boating accident on Florida's intracoastal waterway. It illustrates the role of back-extrapolation and weight-of-evidence (WOE) in an alcoholic impairment assessment and demonstrates how behavior and judgment on the part of the defendant can be considered as evidential in a toxicological analysis... (more)
This case study summarizes a matter in which a group of campers were overcome by carbon monoxide poisoning. It illustrates the importance of taking the initiative to acquire necessary objective evidence to refute presumptions through a scientifically credible toxicological assessment.... (more)
|This case study summarizes the events leading up to and following a widespread contamination case involving local residents and a company disclaiming responsibility for damages. It illustrates the role of weight-of-evidence (WOE) in a toxicological analysis and demonstrates how meticulous attention to detail can be a deciding factor in a complex assessment... (more)
|This case study recounts the circumstances surrounding a woman's claims that exposure to a chemical stripping agent caused burns, infection and damage to her immune system. The outcome illustrates the importance of validating claims against medical history and assessing toxicological factors according to peer-reviewed literature in order to establish reasonable... (more)
|This case study summarizes the events following the death of an elderly man involved in a motor vehicle accident and demonstrates how pharmacological factors and behavior on the part of the defendant can be considered as evidential in a toxicological analysis... (more)
|This case study recounts the circumstances relating to a teacher faced with pending dismissal for alleged drug use based on erroneous interpretation of cocaine in hair test samples. This case illustrates the importance of applying a correct, peer-reviewed scientific methodology to laboratory analyses and interpreting the results in line with established... (more)
|This case study demonstrates how causation can be demonstrated by weight-of-evidence (WOE) and how objective investigation of contributing factors can play a pivitol role in formulating an expert opinion to reasonable toxicological certainty. Toxic encephalopathy can be caused by repeated exposure to high-level refinery hydrocarbon vapors. A process engineer worked for seven... (more)
|This case study illustrates the role of toxicological weight-of-evidence (WOE) in a case involving exposure to mold inside a motor home. It also illustrates how analytical measurements and medical history can be considered as evidential in a toxicological analysis. Shortly after purchasing a new motor home, the owner noticed... (more)
|This case study summarizes events relating to the death of a man with a history of seizure disorder who was fatally exposed to pesticides in his unventilated basement apartment. It illustrates the role of an impartial toxicological assessment in litigation involving pesticides... (more)
|This case study reviews a residential contamination case involving local residents exposed to water contaminated with PAHs and PCBs flooding their properties. It illustrates the importance of applying generally-accepted, peer-reviewed toxicological assessment methods and the steps necessary to present scientifically credible findings in litigation.... (more)
|This case study illustrates the role of toxicological weight-of-evidence (WOE) in a motor vehicle accident case involving polypharmacology and antidepressants. It also illustrates how drug interactions can be considered evidential in a toxicological causation assessment. On the evening prior to a serious motor... (more)
|In this case study, a passenger severely injured in a motor vehicle fire filed a lawsuit against the vehicle manufacturer. The case partially rested on whether or not the driver could be shown to have been intoxicated. The surprising outcome was based on a little known but well-documented fact concerning endogenous alcohol which can be created following... (more)
|This case study summarizes the events surrounding the filing of a lawsuit by residents against a company for allegedly contaminating the local water supply with trichloroethylene, a chemical used in industrial cleaning and degreasing. It further illustrates how exposure evidence, historical factors, a residential questionnaire and a toxicological risk... (more)
|This case study summarizes the events leading up to and following the filing of a lawsuit by a woman against her employer for an injury allegedly suffered as a consequence of a toxic exposure to a cleaning chemical. It illustrates the important role a toxicological assessment can play in litigation and demonstrates how inference and assumption can... (more)
|This case study summarizes a matter in which a window worker was killed while on the job, resulting in the filing of a lawsuit for negligence. It illustrates how toxicological interpretation of historical factors and application of... (more)
|This case study summarizes a recent matter in which a worker was injured while on the job, then later denied Workmen's Compensation benefits when drug use was alleged. It illustrates the key importance of rebutting presumptions... (more)
Notes and References
- National Institute of Justice, "Forensic Toxicology," 2014
- University of Florida Levin College of Law, "Frye v. United States, 293 F. 1013, 1014," DC Cir. 1923
- TCAS demonstrative (redacted), graphical image © Copyright 2017, TCAS, LLC.
- Thumbnail images from multiple sources as noted on referenced pages.