The _inquisitio generalis_ being concluded, and prisoners obtained either by voluntary self-denunciations or on the information of others, the judge, according to canonical usage, had a choice of expedients. He could either proceed to an _inquisitio specialis_ or make use of the method of _purgatio canonica_. The second method had been solemnly adopted by the Church in 803.[378] It was an appeal to God. The accused solemnly swore by the Gospels that he was innocent, while those of his friends or neighbours willing to support him acted as his _compurgatores_ and gave similar solemn testimony to his innocence, their number, from two or three to forty, varying in accordance with the degree of suspicion existing against him. The device was obviously defective. Its only advantage lay in the impressiveness of its appeal to the devout mind, persuaded of the heinousness of the sin of perjury, while it allowed the innocent man to suffer, if he happened to be unpopular and could not prevail upon the necessary number of compurgators to assist him, and also allowed the guilty to go free, so long as he was not over-scrupulous as regards perjury and had the necessary popularity to persuade, or power to compel, others to act as his compurgators. Thus, while the system of canonical purgation was never abolished, it had fallen into virtual desuetude before the end of the thirteenth century.[379] In practice the _inquisitio generalis_ was followed automatically by the _inquisitio specialis_. The accused was served with a citation to appear before the tribunal and kept in prison pending his trial.[380]