Prosecution’s Deductions from Post-mortem Analysis Misleading
The evidence of the prosecution in connection with the analysis was thoroughly unreliable and misleading. Dr. Stevenson’s difficulty was that, while two grains of arsenic was the smallest quantity capable of killing, the analyst had found only one-tenth of a grain, or the twentieth part of the smallest fatal dose, and, in substance, Dr. Stevenson proceeds to argue as follows:
(a) I found 0.015 grain of arsenic in 8 ounces of intestines. (There is no record as to what part of the intestines he examined.) I have weighed the intestines of some other person (not Mr. Maybrick), and find their entire weight to be so much. If, then, 8 ounces of Mr. Maybrick’s intestines yield 0.015 grain, the entire intestines (calculated from the weight of some one else’s intestines), had I analyzed them, would have yielded one-eleventh of a grain.
(b) Dr. Stevenson then proceeds to argue: “I found 0.026 grain of arsenic in 4 ounces of liver. The entire liver weighed 48 ounces, therefore the entire liver contained 0.32 grain of arsenic.”
(c) Dr. Stevenson argues further: “The intestines and liver, therefore, may be taken to contain together four-tenths of a grain of arsenic, and, having found four-tenths of a grain, I assume that the body at the time of death probably contained a fatal dose of arsenic.”
Such was the deduction Dr. Stevenson arrived at, necessitating the assumption that arsenic was equally distributed in the intestines and liver, whereas it is within the personal knowledge of eminent men (such as Drs. Tidy and Macnamara) that arsenic may be found after death in one portion of the intestines, and not a trace of it in any other part. That in arsenical poisoning the arsenic may be found in the rectum and in the duodenum, and in no other part, is beyond dispute, and the fallacy of Dr. Stevenson’s process must be self-evident.
The witnesses for the prosecution themselves supply the proof of the unequal distribution of the arsenic in the liver.
Mr. Davies calculates the quantity in the whole liver as 0.130 grain.
Dr. Stevenson, in his first experiment, puts it at 0.312 grain, and in his second experiment at 0.278 grain; in other words, Dr. Stevenson finds double in one experiment and considerably more than double in another experiment, the quantity found by Mr. Davies, and it is upon this glaring miscalculation and discrepancy that the case for the prosecution was made to rest, and Mrs. Maybrick was convicted.
But with all this miscalculation the approximate amount of arsenic can only be swelled up to four-tenths of a grain, less than one-fourth of a fatal dose, and it was demonstrated that every other part of the body, urine, bile, stomach, contents of stomach, heart, lungs, spleen, fluid from mouth, and even bones, were all found to be free from arsenic.