Principles and Procedures in Forensic Toxicology

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Introduction

Forensic toxicology concerns the application of toxicology to situations that may have medicolegal review, and as a consequence, results must stand up to scrutiny in a court of law.1 There are primarily three subdisciplines of forensic toxicology:

  • 1

    Postmortem toxicology, more recently referred to as death investigation toxicology.

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    Behavioral or human performance toxicology, which concerns

    • a

      Impaired driving as a result of alcohol and/or drugs consumption.

    • b

      Drug-facilitated sexual assault cases.

    • c

      Doping control. Screening of athletes for performance-enhancing substances is monitored by the World Anti-Doping Agency.2 In this category must be included equine and canine toxicology testing, because entire laboratories are dedicated to this specific purpose.

  • 3

    Forensic workplace drug testing or drug urinalysis, which is performed as a preemployment and/or random monitoring of employees for illicit drugs or court-ordered testing of convicted drug offenders.

Closely related but in a category of its own is forensic drug chemistry.3 This discipline is concerned with drug and chemical analysis, as is toxicology, but in regard to nonbiological specimens such as seized bales of marijuana, packets of synthetic cannabinoids, pills, “meth lab” reagent analyses, rocks of crack cocaine, and the like. Toxicology and drug chemistry laboratories often work together on different aspects of a case, especially when the laboratories are housed in the same facility. An important consideration when laboratories are in the same building is that extraction of drugs by each discipline must be accomplished in different rooms to avoid possible contamination of toxicology specimens by the relatively massive quantities of drug chemistry specimens.

To assist with the practice of forensic toxicology, a guide as to how the discipline should be performed is provided in the form of forensic toxicology laboratory guidelines, prepared by the Society of Forensic Toxicology (SOFT) and the Toxicology Section of the American Academy of Forensic Sciences (AAFS).4 Also, at the time of this writing, a “draft” document entitled Scientific Working Group for Forensic Toxicology (SWGTOX) Standard Practices for Method Validation in Forensic Toxicology has been released for public comment. The practice of urine drug testing is defined by Mandatory Guidelines for Federal Workplace Drug Testing Programs, issued by the Department of Health and Human Services.5 This review is restricted to the subdisciplines of postmortem and behavioral toxicology.

Section snippets

How Forensic Toxicology Differs from Clinical Toxicology

Clinical toxicology is typically hospital-based, with the emergency room physicians being the primary customers. Analytical results must be obtained with speed to help confirm the therapeutic regimen for living patients, and an initial screen result by itself is sufficient for use in medical evaluation. Clinical analysts rarely are called about judicial matters, compared with forensic analysts. Quantification and confirmation of drug findings are not usually relevant to the treatment and often

Certification and Accreditation

Forensic toxicology and all fields of forensic science are currently experiencing a period of accelerated change. The impetus for change came in 2009 with the National Academy of Sciences report6 on the need for overhaul of forensic sciences in the United States. A major recommendation of this report was that forensic scientists should be certified in their specific discipline and laboratories should be accredited. Forensic toxicology certification is available primarily through two

Chain of Custody

In that the results of forensic toxicology testing may be used in court proceedings, the first necessary component of the testing process is to demonstrate the validity of test specimens. This demonstration is accomplished through the chain of custody,14 which documents the chronologic disposition and condition of specimens from the time of collection to the time of disposal. The person initiating the chain of custody would typically provide the identity of the individual from whom the specimen

Principles of Quality Assurance

A quality assurance (QA) program is required to ensure that the laboratory produces consistently reliable drug/chemical identification and quantitation. Aspects of a QA program include

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    Competent analyst with access to continuing education. The number of analysts must be sufficient to handle the workload and provide testing services requested. If resources allow it, each analyst would ideally attend a national or international meeting each year. Certification in forensic toxicology should be

Postmortem Investigation

A strong forensic axiom is that no aspect of a death investigation is performed in isolation. There is communication with all staff members through a morning “viewing meeting” to discuss case history, medical records, pharmacy records, and the circumstances of the death. An important consideration is that “results of toxicology testing have to make sense” in light of the entire case findings. For example, GC/MS analysis of specimens and identification of cocaine with no detectable cocaine

Summary

This article is intended to provide the reader an overview of principles, procedures, and practices in a modern forensic toxicology laboratory. Future trends in forensic toxicology may include a change in analytical procedures where LC tandem mass spectrometry, time of flight mass spectrometry, and/or capillary electrophoresis are the standard analytical methods. Certification of analyst and accreditation of laboratories will be a universal requirement. Laboratories will be able to minimize the

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References (51)

  • The American Board of Forensic Toxicology home page

  • The Forensic Toxicology Certification Board home page

  • Programs of accreditation

  • Forensic Quality Services home page

  • Substance Abuse and Mental Health Services Administration home page

  • National Association of Medical Examiners home page

  • College of American Pathologists home page

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