The crime of poisoning, from its nature, must always be a secret one. But little apprehension need be entertained of the art of secret poisoning as understood by Toffana or Brinvilliers,[[63]] or as it might be improved by a modern imitator. It seems to have escaped the attention of those who have written on the subject, that the practice of such an art requires the knowledge not only of a dexterous toxicologist, but also of a skilful physician; for success must depend on the exact imitation of some natural disease. It is only among medical men, therefore, and among the higher orders of them, that a Saint-Croix can arise now-a days. How little is to be dreaded on that head is apparent from the domestic history of the European kingdoms for the last half century, compared with their history some centuries ago. Few medical men have even been suspected, and those few only upon visionary grounds, and under the impulse of violent political feeling.[[64]] In one late instance only, so far as I am aware, has it been proved that the physician’s art was actually prostituted to so fearful a purpose; and the detection of the crime in that case shows how difficult concealment will always be wherever justice is administered rigorously, and medico-legal investigations skilfully conducted.[[65]]
Two extraordinary incidents which happened lately in Germany may appear at first sight at variance with these views. I allude to the cases of Anna Margaretha Zwanziger and Margaretha Gottfried, which justly excited much interest where they occurred, and are notorious to continental toxicologists. Zwanziger, while serving as housekeeper in various families in the territory of Bayreuth in Bavaria during the years 1808 and 1809, contrived to administer poison,—sometimes under the instigation of mere revenge or spite, sometimes for the purpose of clearing the way for her schemes of marriage with her masters,—to no fewer than seventeen individuals in the course of nine months; and of these three died.[[66]] Gottfried, a woman in affluent circumstances and tolerable station in the town of Bremen, was even more successful. For she pursued her criminal career undiscovered for fifteen years; and when detected in 1828 had murdered actually fourteen persons, and administered poison unsuccessfully to several others. Her motive, as in the case of Zwanziger, was the mere gratification of a malevolent temper, or the removal of supposed obstacles to her matrimonial dreams. In neither of these instances, however, did the criminal possess any particular skill, or observe much measure in her proceedings. The cases of poisoning were of the common kind,—produced by arsenic,—proving in general quickly fatal,—and presenting the ordinary phenomena. I cannot help thinking, therefore, that the events now alluded to prove rather the ineffectiveness of the police where they happened, than the adroitness of the actors by whom they were brought about; and that they constitute no sound objection to the statement, that the art of secret poisoning is now unknown, and is not likely to be again revived.
It must be granted, indeed, that the late discoveries in chemistry and toxicology have made poisons known which might be employed in such a way as to render suspicion unlikely, and to baffle inquiry. But the methods now alluded to are hitherto very little known; they cannot easily be attempted on account of the rarity and difficult preparation of the poisons; they can never be practised except by a person conversant with the minute phenomena of natural disease; and it is no part of the object of this work to make them public.
The evidence, by which the medical jurist is enabled to pronounce on the existence or non-existence of poisoning in general, and to determine the subordinate questions that relate to it, is derived from five sources,—1, the symptoms during life; 2, the appearances in the dead body; 3, the chemical analysis; 4, experiments and observations on animals; and 5, certain moral circumstances, which are either inseparably interwoven with the medical proof, or cannot be accurately appreciated without medical knowledge.
Section I.—Of the Evidence from Symptoms.
Not many years ago it was the custom to decide questions of poisoning from the symptoms only. Till the close of last century, indeed, no other evidence was accounted so infallible: and for the simple reason, that in reality the other branches of evidence were even more imperfectly understood. So lately as 1763, and even in Germany, the solemn opinions of whole colleges were sometimes grounded almost exclusively on the symptoms.[[67]] About that time, however, doubts began to be entertained of the infallibility of such evidence; these doubts have since assumed gradually a more substantial form; and it is now laid down by every esteemed author in Medical Jurisprudence, that the symptoms, however exquisitely developed, can never justify an opinion in favour of more than high probability.[[68]] In laying down this doctrine medical jurists appear to me to have injudiciously confounded together actual symptoms with their general characteristics. If the doctrine is to be held as applying to the evidence from symptoms, only so far as they are viewed in questions of general poisoning,—that is, as applying to the general characters merely of the symptoms,—it is deduced from accurate principles. But if it is likewise to be applied, as recent authors have done, to the actual symptoms produced by particular poisons, and in all cases whatever of their action, then it is a rule clearly liable to several important exceptions. These exceptions will be noticed under the heads of the mineral acids, oxalic acid, arsenic, corrosive sublimate, nux vomica, &c. At present it is only the general characters of the symptoms, and the points in which they differ from the general characters of the symptoms of natural disease, that I propose to consider.
The chief characteristics usually ascribed to the symptoms of poisoning considered generally, are, that they commence suddenly and prove rapidly fatal,—that they increase steadily,—that they are uniform in nature throughout their course,—that they begin soon after a meal,—and that they appear while the body is in a state of perfect health.
1. The first characteristic is the suddenness of their appearance and the rapidity of their progress towards a fatal termination. Some of them act instantaneously, and the effects of most of them are in general fully developed within an hour or little more. But this character is by no means uniform. The most violent may be made to act, so as to bring on their peculiar symptoms slowly, or even by imperceptible degrees. Thus arsenic, which usually causes violent symptoms from the very beginning, may be so administered as to occasion at first nothing more than slight nausea and general feebleness; and afterwards in slow succession its more customary effects. In like manner corrosive sublimate may be given in such a way as to cause at first mild salivation, and finally gangrene of the mouth. Even many vegetable poisons might be administered in the same way. The well-known consequences of digitalis in medicinal doses will serve as a familiar instance. A still better illustration is supplied by the medicinal effects of the alkaloid of nux-vomica, whose action in other circumstances is most rapid and violent: Strychnia in a moderate dose will cause death by violent tetanus in two or three minutes; but when given in frequent small doses as a remedy in palsy, it has been known to bring on first starting of the limbs, then stiffness of the jaw, afterwards pain and rigidity of the neck; and these effects might be increased so gradually, that the patient would seem to die under ordinary tetanus. Nevertheless, the foregoing considerations being kept always in mind, it still remains true, that the effects of poisons for the most part begin suddenly, when the dose is large. This is an important circumstance in regard to certain active poisons, such as the mineral acids, oxalic acid, arsenic, strychnia, &c. For when it is considered that in criminal cases they are given for the most part in unnecessarily large doses, it follows that if the effect ascribed to these poisons in such doses have not begun suddenly, the suspicion is probably incorrect.
The same remarks may be applied to the sudden termination of the symptoms. Poison is for the most part given criminally in doses so large that it proves rapidly fatal. Yet this is not always the case; the diseased state occasioned by poisons has often been prolonged, as will be seen hereafter, for several weeks, sometimes for several months; nay, a person may be carried off by a malady, the seeds of which have been sown by the operation of poison years before.
The present would be the proper place for noticing the important question regarding the interval of time, after which, if death supervenes, it cannot be laid to the charge of the person who administered the poison. It is unnecessary, however, to say much on the subject. According to the English law, death must take place within a year. As to the Scottish law, it may be inferred from what has been said by the late Baron Hume on the subject of homicide generally, that a charge of poisoning is relevant although the person should die at a period indefinitely remote, and that it will infer the pains of law, provided the operation of the poison can be distinctly traced, unmodified by extraneous circumstances, from the commencement of the symptoms to the fatal termination.[[69]] Of course the influence of these modifying circumstances in lessening the criminal’s responsibility will increase with the interval. The question for the medical jurist to determine in such a case would therefore be, the distance of time to which death may be delayed in the case of poisoning generally, and in that of the particular poison. This question cannot be answered even with an approach to precision, except in the instance of a few common poisons. Most vegetable and animal poisons prove fatal either in a few days or not at all; but some mineral poisons may cause death after an interval of many days. It appears probable that arsenic may cause death after an interval of several months, and it is well ascertained that the symptoms of poisoning with the mineral acids have continued uninterruptedly and without modification for eight months, and then terminated fatally.