7: Medicolegal Interpretive Toxicology

INTRODUCTION

One of the potential areas of collaboration for toxicologists is the medicolegal setting. This includes working with forensic toxicologists, medical examiners, law enforcement, lawyers, and regulators. In this arena, interpretive toxicology, whether based on analytical findings or theoretical concepts, is routinely used or required to explain issues in criminal and civil proceedings and as the basis for policy making. Often, the concepts associated with forensic interpretive toxicology are presumed to be associated with deceased individuals. In practice, the preponderance of cases involving toxicologic interpretation involves living people and includes specialty testing such as human performance toxicology. Regardless, interpreting the role, or potential role, of xenobiotics in an adverse outcome is typically not straightforward. For example, the use of generally applied pharmacokinetic equations is usually inappropriate, especially in the postmortem setting, yet such is in widespread practice by individuals unfamiliar with the nuances of case-related issues.²⁷ Rarely is any given case accurately interpreted solely based on toxicologic assessment. As such, forensic interpretive toxicology generally involves an integrative approach that draws on an understanding of case history in addition to analytical, toxicologic, pathophysiologic, and specimen-related issues. Individuals called on to interpret the role of xenobiotics in any given case must understand the factors that affect such interpretations and associated limitations. Furthermore, although difficult in many situations, they should attempt to have their opinions firmly supported by science. Other chapters in this text (Chaps. 6 and 34, Special Considerations: SC2 and SC6) cover much of the basic science associated with interpretive issues. This section is meant to focus on specific issues as they relate to medicolegal (forensic) interpretive toxicology.

CASE HISTORY

It has been reported that case history plays a role in interpreting toxicologic findings in about 70% of cases.²⁴ A number of specific aspects of a case ­history will lead a seasoned toxicologist in a direction that narrows the ­scientific investigative focus and avoids a shotgun approach to deciphering the role of toxicology in an adverse outcome. Table 7–1 lists some of the more important aspects of the case history that should be considered from the outset to begin the interpretive process. Detailed information about the individual should optimally include anthropomorphic information, vocation, hobbies, medical history, timing of events to the extent possible, and other contextual information.¹⁷ As an example of the importance of this information, consider a case in which an individual suspected of drunk driving worked at a company that manufactured chemicals. One of the chemicals known to be handled by the individual was a substance that coeluted with ethyl alcohol in the gas chromatographic assay used to quantitate the blood alcohol concentration. Without his employment history, the potential for an incorrect interpretation of the data might have occurred.