Half-proof (semiplena probatio) was a concept of medieval Roman law, describing a level of evidence between mere suspicion and the full proof (plena probatio) needed to convict someone of a crime. The concept was introduced by the Glossators of the 1190s such as Azo, who gives such examples as a single witness or private documents. In cases where there was half-proof against a defendant, he might be allowed to take an oath as to his innocence, or he might be sent for torture to extract further evidence that could complete the burden of proof.