Range of cases submitted
The range of cases the forensic toxicologist is asked to deal with is typically very broad, although it may be restricted by the expertise and instrumental resources of a particular laboratory or the nature of the cases with which they are authorised to deal. For example, in the areas of workplace drug testing and drug abuse in sport much of the testing is carried out by laboratories with special expertise and that are devoted entirely to this type of work. In the chapters that follow, a broad range of poisons and the techniques used for their analysis will be discussed, together with the types of samples encountered and the advantages and disadvantages that these sample types offer the toxicologist. The forensic toxicologist is most often associated with the investigation of sickness or suspicious deaths where poisoning is suspected, whether it be self-administered or malicious. However, it should be remembered that in many incidents of suspicious death there may be no obvious indication of poisoning from the case history. For example, if an elderly person is found dead at home and the postmortem examination does not reveal an obvious medical cause of death, the coroner will request toxicological analysis even though no drugs or poisons were found near the body. The forensic toxicologist will also receive samples from road traffic accidents to investigate whether alcohol and/or drugs may have been a contributing factor. Laws that govern the possession and use of narcotic and stimulant drugs, and legislation concerned with the influence of drink or drugs on driving skills, have increased the workload of many forensic laboratories; these cases can account for over 70% of the total workload submitted.
Modern analytical methods can give the forensic toxicologist the ability to answer ques tions that previously were considered either hopeless or not worth considering because the results were so often negative. Methods that are sensitive to nanogram amounts of drugs and poisons make it worthwhile to undertake an analysis, even when the plate, cup or container involved has apparently no food or drink left in it. Drugs may be detected in blood at therapeutic concentrations, so it is possible to obtain clues to the clinical history of the deceased, the victim or the accused, even when they are unable or unwilling to provide this information for themselves. Thus, the discovery of drugs used in the treatment of epilepsy, diabetes, etc., in a blood sample taken from an unidentified body may start a new train of inquiries that leads to successful identification of the body. Similarly, allegations of doping prior to rape or robbery may be refuted or confirmed.
A newer form of forensic toxicology concerns the analytical checking of statements made by witnesses during the course of a police inquiry. Provided that a blood or urine sample is taken within about 12 h of an event, there is a good chance of checking the truth of statements such as ‘I don’t remember what happened because I was high on drugs at the time’, ‘I used to be an addict, but I haven’t taken anything for over a year’, ‘I killed him in self defence because after taking LSD he went berserk and attacked me with a knife’, ‘He spiked something into my drink, I don’t remember much after that but I think he raped me’. Stains can also be examined successfully for drugs and poisons. For example, if the victim notices a nasty taste and spits out the drink, the allegation that someone had tried to poison him or her can be investigated if the stain is submitted for analysis. In most cases, the results obtained in the various types of cases mentioned above can be proved conclusively, that is the identity of the poison can be confirmed by more than one method and it can be quantified. Even when specific identification is not feasible, an opinion as to whether the suspect is most probably telling the truth or lying can be of value to the investigator.
