Magna Carta
<c.38> Nuls bailliz ne mette des ci en avant alcun a lei par sa simple parole, fors par bons tesmoinz amenez a ice (Nullus ballivus ponat decetero aliquem ad legem simplici loquela sua, sine testibus fidelibus ad hoc inductis). From this time forward no bailiff shall bring anyone to court on just his authority alone, unless good witnesses provide evidence.
De rege Johanne, British Library, Cotton Claudia D.ii. folio, fol. 116r
Ex quibus auctoritatibus manifeste probatur, quod non solum, cum subditus, verum etiam, cum prelatus excedit, si per clamorem et famam excessus eius ad aures superioris pervenerit, non quidem a malevolis et maledicis, sed a providis et honestis, nec semel tantum, sed sepe, quod clamor innuit et diffamatio manifestat, debet coram ecclesie senioribus veritatem diligentius perscrutari. From these authorities it is clearly shown that not only when a subject has committed a crime but also when a prelate perpetrated a crime, and the matter reaches the ears of a superior through gossip or rumor that comes not from evil and slander but from prudent and honest persons and comes not only once but frequently, because rumor gives evidence and evidence becomes manifest, the prelate ought to examine the evidence diligently with the important clerics of his church.
Richard H. Helmholz, “Magna carta and the ius commune,” The University of Chicago Law Review 66 (1999) 297-371
Ken Pennington, “The Ius commune, Suretyship, and Magna carta,” Rivista internazionale di diritto comune 11 (2000) 255-274