A case of wide interest and unusual circumstance which set the south Canterbury centre of Timaru agog in the 1880s was that of Thomas Hall, a young businessman who was convicted in 1886 of the attempted murder by poisoning of his wife, and in the following year had a verdict of guilty of the murder of his father-in-law, Captain Henry Cain (also by poisoning), quashed by the Court of Appeal because the only real evidence against him was his unsuccessful attempt on his wife's life. On a case reserved by the Judge (Mr Justice Williams, who had sentenced Hall to death) the Court of Appeal held that as there was not sufficient proof that the two poisonings formed part of the same transaction, or were effected in pursuance of a common design, the conviction must be quashed.

Hall first appeared in Court in October 1886 when he faced an attempted murder charge. The trial lasted eight days and he was sentenced to life imprisonment for what Mr Justice Johnston described as a crime that had been committed from “hour to hour, day to day, and week to week”. Hall, the year before, had married a young woman of means and even greater expectations, but almost from his wedding day he found himself all but submerged by a flood of debts, overdrafts, and defalcations which made the acquisition of a large sum of money essential. His wife's death seemed to be the answer. He insured her for £3,000 and persuaded her to make a will in his favour. In the meantime he had provided himself with Taylor on Poisons and fairly generous supplies of antimony and colchicum, both deadly poisons. These he began to administer systematically to his wife after she had been delivered of their first child. It was a long time before the family doctor could convince himself of the truth of what was going on almost under his nose, but Hall was finally arrested. The evidence, which included the discovery of a phial of antimony in Hall's pocket when he was apprehended, was overwhelming, and it took the jury seven minutes to find him guilty.

In the meantime, however, a month before, the police had exhumed the body of Captain Cain, who had died in January 1886. Hall had been a constant visitor at Cain's bedside for several weeks before his death. When, after exhumation, Cain's body was found to contain traces of antimony, Hall was brought from prison and in January 1887 was tried at Dunedin for murder. The Crown was handicapped by lack of evidence but presented the sordid story of his poisoning of his wife. The admissibility of such evidence was vigorously challenged by the defence, but Mr Justice Williams told the jury: “You have a perfect right to take all these circumstances into account…. If antimony is found in the body of a person to whom the prisoner has access, and if later antimony was without doubt administered by him to another person, it is for you to say if it is not a reasonable conclusion that the antimony found in the body of the first-named person was also administered by the prisoner”.

His Honour incidentally conceded that, without the testimony relative to Mrs Hall, there was insufficient evidence for any reasonable jury to convict. The jury did convict, and His Honour pronounced the death sentence; but at the same time he reserved for the Court of Appeal the question of the admissibility of the vital evidence. The Court of Appeal, presided over by the Chief Justice, Sir James Prendergast, quashed the conviction because, in the words of Mr Justice Johnston, who delivered the judgment of the Court: “In fine, the strong moral probability that the prisoner, as he was the agent in the one occurrence, also brought about the prior event, is not the kind of proof of guilt which the English law exacts – it is indeed a kind of proof which the English law, rightly or wrongly, rejects and excludes.”

So Thomas Hall escaped the scaffold and was returned to his prison cell.