ABSTRACT
Drugs and alcohol influence lives in many ways. Many practitioners believe that precise laboratory measurements can supply information that could not have been gathered by accurate history and scene investigation alone. Each investigative modality has its contribution to make to a forensic investigation. There are a number of misunderstandings concerning toxicology, and failure to consider them can lead to needless effort and expense, not to mention an incorrect conclusion. In death, concentrations in whole blood are measured. Drug concentrations, especially the concentration of alcohol, are different in plasma and whole blood. Serum and plasma contain 10–15% more water than whole blood. Vitreous humour is a useful testing medium, especially for the diagnosis of electrolyte disorders, renal failure, hyperglycaemia and ethyl alcohol ingestion. Measurement of alcohol concentrations in the vitreous humour may even help distinguish between post mortem alcohol formation and ante mortem ingestion.
