Expert witnesses are people who are hired, based on their training, education and expertise, to testify at civil or criminal proceedings. They have knowledge of a particular subject that goes beyond that of an average person or lay witness. A toxicology expert witness has expertise and education in toxicology, the study of the effects chemicals have on living beings. The chemical in question could be alcohol, poison, prescription medications, illegal drugs, tobacco, pesticides, or any other chemical substance that could affect a human, whether positively or negatively.
The role of a toxicology expert witness will vary from case to case. A toxicologist may be called to support or refute evidence or facts of a case. Testifying toxicology experts will review the case and provide their unbiased opinion to support or refute the cause of the reaction or non-reaction a chemical had on a perpetrator, victim or witness. The toxicology expert may help the prosecutor or defense attorney prepare questions for opposing forensic expert witnesses. An attorney may rely on a forensic expert to explain a scientifically complex interaction of a chemical with a human in terms the attorney, judge and jury can all understand.
There are qualifications a toxicology expert witness should have to be able to fulfill his duties. A forensic toxicologist needs to have extensive experience and knowledge of the medical effects — both physical and mental — chemicals have on the human body. A toxicologist’s expertise may be specific to a particular type of chemical or more general. The lawyer will need to make sure the background of the toxicology expert witness matches the factors in the case, and that his motives are pure; otherwise the expert could be deemed unqualified, biased, or unreliable.
The judge is ultimately the one who determines if a toxicologist is qualified to be a toxicology expert witness. A toxicologist needs to be able to apply generally accepted toxicological, scientific and medical principles to the case. Having a forensic toxicologist who has been deemed an expert by other judges in the past can make this process smoother. With or without such a past determination, judges will consider education, years of experience, expertise specific to the chemical and medical reactions in question, writings, teachings, and lack of potential bias of the individual.
Being qualified knowledge-wise is not the only attribute a forensic expert is expected to have. Expert witnesses need to be seen as confident, knowledgeable, and sure of their testimony, without appearing pretentious, condescending, or arrogant. They need to be skilled, both in their areas of expertise and in clear, direct communication. The judge and jury should be able to understand the concepts the experts are explaining, concur that the experts have the credentials to back up their testimony, and have faith that the toxicologists believe the facts to which they are testifying.