There is always more to say, of course, but I answered an earlier question on the Devil's Advocate here a while ago, and this went into some detail as to how the system worked. You might like to review that earlier answer while you wait for fresh responses to your query, but it does explain that the process was an official one and internal to the Catholic church; moreover, it involved the compilation of complex written dossiers of evidence over periods of a decade or more, for eventual review by senior church authorities – it wasn't as though these lawyers would appear in public and attempt to demolish the reputation of beloved candidates for sainthood in front of groups of people who had known them:

Do we know of any cases in the Catholic Church when the Advocatus Diaboli (or Devil's Advocate) successfully argued against someone becoming a saint?