The Canons of the 217 Blessed Fathers who assembled at Carthage 130

130 Canon CXXX

That he who has failed to prove one charge shall not be allowed to give evidence to another.

So, too, it seemed good that as often as many crimes were laid to clerics by their accusers, and one of the first examined could not be proved, they should not be allowed to go on giving evidence on the other counts.

Ancient Epitome of Canon CXXX.

He who makes many accusations and proves nothing [is not to give witness].

Philip Schaff and Henry Wace (eds.), New York: Christian Literature Publishing Co., 1890-1900. Public domain: English translation first published 1885-1900 (Nicene and Post-Nicene Fathers, Second Series).