Sir Charles Imphery

In the novel Cards on the Table, Sir Charles Imphery is the Home Office Analyst. Poirot mentions him during the denouement, when he is explaining that the murderer had injected Mrs Lorrimer with a drug known as Evipan, which is dangerous to use after veronal or other barbiturates have been taken. This is what caused her death. Poirot had hinted this to the police surgeon, resulting in Sir Charles easily discovering the drug in the body of Mrs Lorrimer.