Two autopsy cases of an elderly couple who died on the same day will be used to underline the importance of immunohistochemistry of forensic practice. At first unexplainable injection marks on the upper arms of the corpses and the possibility of a closely related physician injecting insulin and certifying a natural death made it important, considering suspect insulin concentrations in the blood, to exclude insulin injections in these marks. Further, the statement that morphine had been injected for the analgesia of tumour pains, was reinforced by immunohistochemistry.