A forensic toxicological dilemma: the interpretation of post-mortem concentrations of central acting analgesics

Dora V., a 88-year-old pensioner suffering from a hiatus hernia, died at the home of an orthopaedist and his wife, an anaesthetist, immediately after she had received a dose of 300 mg pethidine via intravenous infusion in a timeframe of about 90 min. One day before her death a befriended notary of the couple visited Dora V. and obtained a blank signature. After her death, a will was forged using this signature, rendering the couple sole heirs of Dora V.'s estate with a value of several million euros. Post-mortem toxicology was performed in three different institutes of legal medicine. The concentrations of pethidine in peripheral venous blood were between 6.1 and 6.5mg/l and 9.5 and 17.2mg/kg in brain. Pharmacokinetic calculation confirms the given dose. There was no doubt that the cause of death was acute pethidine intoxication. The accused couple claimed that this dose of pethidine was indicated to relief pain, and as the pathologists said in their expert opinions that the hiatus hernia could explain her death, the court had to acquit the accused. This very special case demonstrates that preconceived murder of a sick person with suitable analgesics cannot be proven--at least not with the methods available to forensic toxicology and pathology. This has to be taken into consideration if euthanasia will be legalised under special circumstances.