Why and when is forensic toxicology used in death investigations?
In post-mortem investigations, suspected drug overdoses are clear situations where toxicology is required to establish if an excessive intake of the drug occurred and, if so, whether this contributed to death. Conversely, toxicology can eliminate the possibility of a drug overdose if concentrations are not capable of causing death, given all other factors. This means that toxicology testing can produce a positive result even in cases where drug use is not mentioned in the police circumstances. This is not surprising given the wide availability of potentially toxic substances, both legal and illegal. In addition, concentrations of substances change after death making any interpretation difficult, no matter the concentration.
In many cases, poisons may be detected by the toxicology laboratory but are not necessarily a cause of death, rather their presence may be relevant in the circumstances of death. For example, alcohol and impairing drugs are found in about half of all drivers killed in motor vehicle crashes in Australia, nearly one-third (31%) of all traffic-related deaths in the United States and in a significant proportion of other accidental deaths. Alcohol and/or drugs are also found in a significant number of other deaths reported to the coroner; for example, in suicides that include non-drug related intentional deaths. In death cases where natural disease is partially to blame, drugs that indicate an underlying disease are often detected, such as drugs that have been used to treat a condition or pain. Sometimes these drugs are regarded as contributing to the cause of death.
Regardless how the individual died, toxicology testing can determine whether levels of toxic substances may have contributed to this death.