Hilchos Lashon Hara chapter 7, section 13

Sometimes, in specific cases, if someone comes to a beis din and says someone stole from him and there are absolutely clear indications supporting this which the beis din saw for themselves or heard from witnesses, the beis din may strike the thief to make him confess. But an individual or a beis din that only heard the devarim nikarim from the plaintiff himself do not have this leniency.