THE ELEMENT
The Chemistry of Autopsy When a person dies, their body cycles through four stages of death. First comes pallor mortis. Within 15-30 minutes of death, capillary circulation collapses and the skin goes pale (an effect most prominent in those with light skin). Pallor mortis is quickly followed by algor mortis during which the body cools to match the temperature of the surroundings and as the body cools, the muscles stiffen and the body grows rigid, a phenomenon known as rigor mortis. Six to eight hours later, the final stage of death takes hold of the body- livor mortis. A stage characterised by the pooling of the blood to certain areas of the body due to the force of gravity. These four stages are often quite helpful in determining the time of death, but to gain more insight into how someone has died, autopsies or post-mortem exams are performed. An autopsy involves the examination of the external body, the internal organs and the substances that lie within them. Let's take a look at this case example: “A 55 year old male is found deceased in a bed in a secure residence . There is an antidepressant medication on scene next to the bed including the tricyclic antidepressant imipramine. In addition, there is a half full bottle of wine on the floor. At autopsy, the medical examiner can find no immediate anatomical cause of death. The medical examiner submits venous 24
blood, heart blood, vitreous humor and liver to the forensic toxicologist for analysis.” There are several pieces of important information in this extract, the most prominent of which being the presence of medication and alcohol. This is particularly important as no immediate anatomical cause of death was found by the medical examiner, meaning the cause of death is most likely accessible on a molecular level. The individual’s age and sex will come in useful when interpreting the toxicology results later and as for the submitted specimens, they would be ideally stored between 2-8 degrees celsius to slow distribution and putrefaction (decomposition). Unfortunately, determining whether the imipramine and/or alcohol was responsible for the death is not as simple as measuring the concentrations of the relevant compounds in the specimens, however several other factors must be taken into account. Most prominently, the phenomenon of post-mortem redistribution (PMR). Postmortem redistribution involves the changes in drug concentrations after death. Simply put, a drug’s movement around the body from blood to tissue and tissue to blood after death. The extent to which a drug will display PMR is down to its chemistry. Various drug properties such as volume of distribution, lipophilicity and acid-base
