34: Postmortem Toxicology

INTRODUCTION

Postmortem toxicology is the study of the identification, distribution, and quantification of xenobiotics after death. This information is used to account for physiologic effects of a xenobiotic at the time of death through its quantification and possible redistribution in the body at the time of autopsy. ­Several variables may cause changes in xenobiotic concentrations during the interval between (1) the time of death and subsequent autopsy and (2) the storage interval between the time of sampling and the time of testing. Toxicologists and forensic pathologists are frequently asked to interpret postmortem xenobiotic concentrations and decide whether the reported values are meaningful and whether these xenobiotics were incidental or contributory to the cause of death.

The development of the field of forensic toxicology and the improvement of laboratory technology now permit more refined identification and quantification of xenobiotics. The interpretation of postmortem xenobiotic concentrations and their significance, however, continues to evolve.

This chapter reviews factors that affect xenobiotic concentrations identified at autopsy and discusses an approach for interpreting postmortem toxicologic reports as they relate to the cause and manner of death.^{38,41,43,49, 50, and 51,59,69,79,97}

HISTORY AND ROLE OF MEDICAL EXAMINERS

The relationship between antemortem xenobiotic exposures and death has been a subject of investigation for centuries. In 12th-century England, an appointee of the royal court, eventually named the coroner, was designated to record and identify causes of death.⁷³ In suspicious circumstances, coroners investigated poisonings, but scientific methods were primitive, and conclusions regarding such deaths were conjecture at best.

By the mid-19th century, however, techniques for detecting certain xenobiotics in postmortem tissue were developed and focused generally on identifying heavy metals as a cause of death in homicides.^{44,73,77,94,99} At that time, coroners were still elected or appointed individuals with little or no medical training. However, with better laboratory techniques and autopsies being performed by trained pathologists, the specialty of forensic medicine continued to develop. In late 19th-century Massachusetts, trained pathologists, referred to as medical examiners, ultimately replaced the coroner system and were eventually empowered by the state to investigate certain types of unusual or suspicious deaths (medicolegal autopsies).⁷³ Currently in the United States, legal jurisdiction of death investigations is the responsibility of either a coroner or a medical examiner depending upon the state or county, with 19 states using medical examiner systems almost exclusively.⁴⁸

The medicolegal autopsy, ideally, is performed by a forensic pathologist who attempts to establish the cause and manner of death (Table 34–1). The cause of death is the etiology ultimately responsible for death to occur. For example, the presence of cyanide in the toxicologic evaluation may be sufficient to establish cardiorespiratory arrest from cyanide poisoning. The manner of ...