We will revisit the trial of Galileo and his condemnation for heresy by the Catholic Church. This remarkable historical event, 400 years ago, was the impetus for the ensuing battle between science and religion. I will intend to prove, using only the documents of that time, that Galileo was innocent of the charges. The congregations of the holy office of the inquisition and the index of prohibited books will be studied. Finally, we will examine inquisitional manuals with instructions as to how they conducted an 'inquisitio' (an inquiry), and who was to be charged, who was to be tortured, etc.