An actual case will show that the discovery of murder by the doctor and analyst is not always plain sailing.
A good many years ago, a Mr. Sprague was tried for the murder of the Walker family by means of the well-known poison of the deadly nightshade. The medical evidence showed clearly that they all died from belladonna poisoning, and belladonna was found in the rabbit-pie they had for dinner. A common-sense jury, however, acquitted the prisoner; and only recently have medical men solved the mystery by discovering that rabbits can eat any quantity of this plant without suffering harm, while their flesh becomes fatally poisonous.
A second case shows what wonders the chemists can work. A surgeon's wife died from corrosive sublimate, given in a draught by her husband. He said that, in making up the draught, he mistook a bottle of mixture, which he had prepared for a sailor, for the water-bottle, and had poured some of it into his wife's draught. The sailor's mixture was analysed, and it certainly contained corrosive sublimate; but, not content with finding the poison, the analyst measured the quantity present, and, while the sailor's mixture contained only ten grains to an ounce of liquid, the wife's draught contained fifteen grains, showing that the surgeon's ingenious explanation was a lie!
Blood is so characteristic a fluid that it might be supposed a skilful analyst could never have any difficulty in recognising it. Of course, if he were given, say, a cupful in its ordinary state, he could not make a mistake. But he never gets a chance of earning his fee so easily.
When the police seek his assistance they give him, perhaps, a suit of dirty clothes, which may be stained by two or three small dark spots that might be anything.
Or perhaps he is given a rusty knife, or a perfectly clean hatchet, and is asked to say if there is blood on it. And when he comes into court he is expected to tell the jury whether the blood is human or animal, how old it is, was it spilled from a living blood vessel, and in what part of the body was this blood vessel.
Take an actual case. Years ago a celebrated murder was committed in Eltham, and in the report of Dr. Letheby, the analyst, is the following note:—
"On the evening of May 3rd I received from Mr. Mulvaney" (of the police) "a brown paper parcel containing a pair of dark trousers, a man's shirt, and a man's wide-awake hat. On the following evening I received from Mr. Mulvaney a brown paper parcel containing a lock of hair, a pair of men's boots, and a plasterer's hammer."
These were all very dirty, but that did not prevent the analyst from finding a number of blood stains and hairs, and giving valuable and decisive evidence at the trial.
