Historically, torture has been reviled as an idea, yet employed as a tool and defended by its wielders, often in direct contradiction to their own averred beliefs. Judicial torture was a common feature of the legal systems of many countries including all civil law countries in Europe until the Enlightenment era. A papal bull forbade the practice of torture in Roman Catholic countries in 1816. This was part of ancient Greek and Roman law theory that remained valid in Europe. Roman law assumed, for example, that slaves would not tell the truth in a legal court as they were always vulnerable to threats from their owners. Their testimony could only be of value if it were extracted by a greater fear of torture. Legal scholars were well aware of the problems of false testimony produced by the threat of torture. In theory torture was not meant to produce a confession as such, but rather details of the crime or crime scene which only the guilty party would know.