The evidence of Professor Paul went to prove that arsenic was present in the material of earthenware vessels similar to that in which the lunch was sent to Mr. Maybrick's office, and that it could be liberated by the action of an acid, so that the arsenic found in the particular vessel might have originated from the action of acids in the food itself upon the interior of the vessel.
As has been mentioned, one of the points brought as evidence against the prisoner was that a bottle of glycerine had been found in the lavatory, and that this contained arsenic. There was no evidence that the prisoner had ever had this bottle in her hand, and, apart from that, arsenic is a very usual impurity in ordinary commercial glycerine.
Having regard to the conflict of the scientific testimony, and to the evidence of Mr. Maybrick having acquired the habit of taking arsenic while resident in America, it was generally expected that the prisoner would be acquitted. The judge, however, evidently believing her guilty, summed up strongly against her, and put the point to be decided in the following form: The prosecution said that arsenic was the producing cause of the gastro-enteritis which was the immediate cause of death; arsenic was found in the body, and strong proof was given that arsenic was administered. The terrible question was: By whose hand was it administered? The deceased might have taken it himself, and if there was any reasonable doubt upon that point it was the duty of the jury to acquit the prisoner; but if a crime was committed, no other person but the prisoner was suggested as having committed it.
The jury were so influenced by the remarks of the judge that, after a retirement of a little over thirty minutes, they found the prisoner "Guilty."
The feeling was very widely expressed that the prosecution had failed to establish beyond all reasonable doubt that the deceased had died from arsenic, and that arsenic had been given to him by the prisoner, and that, therefore, she was entitled to the "benefit of the doubt," which the judge's directions to the jury had not allowed to her.
It may be mentioned here that the judge himself, in the second edition of his _Criminal Laws of England_, published in 1890, states that out of 979 cases tried before him up to September, 1889, "the case of Mrs. Maybrick was the only case in which there could be any doubt about the facts."