How did traditional sharia rules determine which side had the burden of proof in a court case?

In traditional sharia, the burden of proof was not automatically assigned to the party who initiated the lawsuit. Instead, the qadi determined which party bore the burden based on which contention contradicted the initial legal presumption of the case.1

For example, in criminal matters, the law presumed the innocence of the accused, placing the burden of proof on the prosecution. In civil suits regarding debt, the law presumed the defendant was free of debt, placing the burden on the claiming creditor.1

This burden was dynamic and could shift between parties during the proceedings, such as when a defendant introduced a counterclaim against the plaintiff. Once the burden was established, the qadi oversaw a formalistic process where the outcome depended on the production of specific shahādah (oral testimony) or the administration of a solemn oath. While this system was largely self-operating, some jurists, such as Ibn Taymiyyah, argued for a more flexible approach that allowed for the consideration of circumstantial evidence to reach a just decision.1