Laws of Lashon Hara / 7: 13-14 (62)

13. One who sues his friend in a rabbinical court, and the judges themselves have ‘recognizable signs’ that prove this person’s guilt, they are permitted to strike him so that he’ll confess. However, an individual or a rabbinical court to which the recognizable signs aren’t evident, it is forbidden.

14. Therefore, one who comes with a complaint against another who has wronged him before leaders of the community, if they do not see these ‘recognizable signs’ firsthand that prove that his complaint is true, they are forbidden to rely on the plaintiff and strike his opponent, so too, they are forbidden to believe him.