Castaing expected, as a result of the doctors' report, immediate release. In this he was disappointed; he was placed under stricter arrest and taken to Paris, where a preliminary investigation commenced, lasting five months. During the early part of his imprisonment Castaing feigned insanity, going to disgusting lengths in the hope of convincing those about him of the reality of his madness. But after three days of futile effort he gave up the attempt, and turned his attention to more practical means of defence. In the prison at Versailles, whither he had been removed from Paris, he got on friendly terms with a prisoner, one Goupil, who was awaiting trial for some unimportant offence. To Goupil Castaing described the cruelty of his position and the causes that had led to his wrongful arrest. He admitted his unfortunate possession of the poison, and said that the 100,000 francs which he had invested he had inherited from an uncle. Through Goupil he succeeded in communicating with his mother in the hope that she would use her influence to stifle some of the more serious evidence against him. Through other prisoners he tried to get at the chemists from whom he had bought acetate of morphia, and persuade them to say that the preparation of morphia which he had purchased was harmless. The trial of Castaing commenced before the Paris Assize Court on November 10, 1823. He was charged with the murder of Hippolyte Ballet, the destruction of a document containing the final dispositions of Hippolyte's property, and with the murder of Auguste Ballet. The three charges were to be tried simultaneously. The Act of Accusation in Castaing's case is a remarkable document, covering a hundred closely-printed pages. It is a well-reasoned, graphic and unfair statement of the case for the prosecution. It tells the whole story of the crime, and inserts everything that can possibly prejudice the prisoner in the eyes of the jury. As an example, it quotes against Castaing a letter of his mistress in which, in the course of some quarrel, she had written to him saying that his mother had said some "horrible things" (des horreurs) of him; but what those "horrible things" were was not revealed, nor were they ever alluded to again in the course of the trial, nor was his mistress called as a witness, though payments of money by Castaing to her formed an important part of the evidence against him. Again, the evidence of Goupil, his fellow prisoner, as to the incriminating statements made to him by Castaing is given in the Act of Accusation, but Goupil himself was not called at the trial.