Death may undoubtedly be due to the action of a poison, and yet its presence may fail to be detected, due to—(1) The nature of the poison-strychnia, hydrocyanic acid, &c. (2) Vomiting and purging. (3) Absorption and elimination. (4) Decomposition—phosphorus, chloral hydrate, chloroform. (5) Smallness of the dose.
(For directions for conducting a post-mortem examination in cases of poisoning, see page 61.)
4. Evidence from Experiments on Animals.—The evidence derived from experiments on animals with the contents of the stomach and vomited matters must not be too implicitly trusted, as these may give rise to vomiting and other symptoms when no poison is present. All animals are not alike affected with man by the same poisons; and it appears that the dog and the cat are the only animals that at all approach man with regard to the effects produced. Experiments on the lower animals are useless to decide—(1) The fatal dose of any poison. (2) The rate of absorption, deposition, or elimination of poisons. (3) The rapidity of the action of certain poisons.
In the case, however, of some vegetable poisons, the effects produced on animals by a portion of the substance taken by the person suspected of having been poisoned, may afford corroborative evidence of poisoning. In the case of Lamson, executed for poisoning his brother-in-law with aconite, experiments on animals formed the chief evidence against the accused.
5. Moral Evidence.—The moral evidence of poisoning is generally furnished by the common witnesses of the Crown; but the value of this kind of evidence, in many cases, can only be fully appreciated by a medical witness. To render this part of the subject as complete as possible, a few remarks may not be out of place. The suspicious conduct of the prisoner before and after the event, the recent purchase of poison, the mode of administration, the object of the prisoner in getting rid of his supposed victim, and the fact of several persons being alike affected, should be carefully noted down. The anxiety evinced during the illness of the deceased, and the hurry in the funeral arrangements, showing an over-anxiety to remove all traces of his guilt, are suspicious. The probability of suicide is weakened by the state of the mind and the nature of the dying declarations of the deceased. In the case of a person indicted for poisoning, evidence to show motive in another case is admissible. (R. v. Geering, 18 L.J. [M.C.] 215; R. v. Heeson or Johnson; R. v. Garner, 3 F. & F. 681.)
Lastly, it remains to be considered—
What is the duty of a Medical Man who suspects the Action of Poison in a Patient on whom he is in attendance?
In the case of R. v. Wooler, Baron Martin, who tried the case, in his charge to the jury, stated that, in his opinion, the medical men in attendance ought, “when the idea of poisoning struck them, to have communicated their suspicion to the husband, if they did not suspect him; and if they did suspect him, they ought to have gone before a magistrate.” Suppose they had acted as the learned judge suggested, and spoken to the husband, who, had he been guilty, would in all probability have desisted from his terrible design for a time, then a great criminal would have been let loose on society, and without punishment. Then, again, had they applied to the magistrates, the delay caused by the indecision of the magistrates how to act in so delicate a case would have allowed the criminal to remove all traces of his design, and the means of testing their suspicions would have been lost; and, along with this, would have been lost the professional character and fortunes of the authors of the investigation. “There is a third course,” said the late Sir R. Christison, “and in my opinion it is the fittest of all: When the medical attendant is satisfied of the fact of poisoning, he should communicate his conviction to the patient himself. His predicament, in every other way, is so embarrassing, that he ought not to be deterred by the chance of injury to his patient from making so dreadful a disclosure.” (See an account of the same course being adopted in the case of Mr. Blandy by his physician, Dr. Addington, reported in Howell‘s State Trials, vol. xviii.)
Table giving the names of Diseases, the Symptoms of which resemble those the result of Irritant Poisons, together with such points of difference as may assist in distinguishing the one from the other:
Irritant Poison.—Symptoms of violent irritation in one or more portions of the alimentary canal. Pricking and burning of the tongue and mouth, and intense thirst, frequently accompanied with great constriction in the throat. Great abdominal pain and tenderness. Vomiting and purging are also usually present. The skin is hot and cold at intervals; the pulse small, frequent, and irregular. In the last stage the skin may become icy cold. An acrid, metallic, or burning taste in the mouth precedes the vomiting. The vomit and alvine discharges are generally mixed with blood. Death occurs in from six hours to two days and a half.