The defence was that the deceased had died a natural death, and that Katharine Nairn was in the habit of taking small doses of laudanum and of salts for her health. Expert evidence was given on her behalf by a Dr. J. Scott to the effect that "he had made experiments upon arsenic and knew well that it would not dissolve in warm water." The evidence, which by the way is incorrect, went to prove that even if arsenic had been introduced into the tea it could not have caused death by poisoning. A surgeon also gave evidence that the symptoms might have arisen from natural causes. For the prosecution no proof of the powder being arsenic or that the husband had really died of arsenical poisoning was given, and no post-mortem examination was made. The counsel for the defence put the position in the following form: "The incest is supposed to be certain because the husband is supposed to have been poisoned; and, on the other hand, the man is believed to have been poisoned, because there is supposed proof of incest." Both prisoners were found guilty and sentenced to death, but the execution was delayed pending an appeal to the Privy Council in London. The sentences were confirmed and Patrick Ogilvie was executed in November, but Mrs. Ogilvie, who was expecting the birth of a child, was kept in prison. A daughter was born early in 1766, and Katharine Nairn managed to escape from prison in March of that year. The trial curiously foreshadowed the trial of Mrs. Maybrick a century later in many of its features, and, as in the modern case, convincing proof of guilt was wanting. * * * * * The question whether a particular substance is or is not a poison has frequently been raised in a court of justice, and on several occasions a prisoner has owed his acquittal to a conflict of scientific opinion upon the point. This was the case in a trial that took place in 1836, at the Norwich Assizes, when two farm labourers were charged with having attempted to poison a fellow farm servant, by putting "a deadly poison," blue vitriol (copper sulphate), into a glass of milk. The man noticed that the milk had a metallic taste and only drank a portion of it; but this was sufficient to make him ill for a short time. On the milk being examined it was found to contain copper sulphate, and suspicion pointed to its having been doctored by the prisoners. The counsel for the defence raised the objection that the accused were indicted for having administered a "deadly" poison, and that medical opinion did not hold that blue vitriol was a deadly poison. A medical witness called on behalf of the prosecution stated that he considered that copper sulphate was a deadly poison, but at the same time admitted that he had no experience of any case of poisoning in which that salt had been taken. On the other hand, another doctor asserted that in his opinion the substance was not poisonous, and pointed out that it was not sold as a poison.