ency of witnesses; yet even here the rigor of the Roman
lawyers relaxed on the necessity of the case. Persons who kept houses of
ill-fame were with them incompetent witnesses; yet among the maxims of
that law the rule is well known of _Testes lupanares in re lupanari_.

In ordinary cases, they require two witnesses to prove a fact; and
therefore they held, "that, if there be but one witness, and no probable
grounds of presumption of some kind (_nulla argumenta_), that one
witness is by no means to be heard"; and it is not inelegantly said in
that case, _Non jus deficit, sed probatio_, "The failure is not in the
law, but in the proof." But if other grounds of presumption appear, one
witness is to be heard: "for it is not necessary that one crime should
be established by one sort of proof only, as by witnesses, or by
documents, or by presumptions; all the modes of evidence may be so
conjoined, that, where none of them alone would affect the prisoner, all
the various concurrent proofs should overpower him like a storm of
hail." This is held particularly true in cases where crimes are secret,
and detection difficult. The necessity of detecting and punishing such
crimes superseded, in the soundest authors, this theoretic aim at
perfection, and obliged technical science to submit to practical
expedience. "_In re criminali_," said the rigorists, "_probationes
debent esse evidentes et luce meridiana clariores_": and so undoubtedly
it is in offences which admit such proof. But reflection taught them
that even their favorite rules of incompetence must give way to the
exigencies of distributive justice. One of the best modern writers on
the Imperial Criminal Law, particularly as practised in Saxony,
(Carpzovius,) says,--"This alone I think it proper to remark, that even
incompetent witnesses are sometimes admitted, if otherwise the truth
cannot be got at; and this particularly in facts and crimes which are of
difficult proof"; and for this doctrine he cites Farinacius, Mascardus,
and other eminent Civilians who had written on Evidence. He proceeds
afterwards,--"However, this is to be taken with a caution, that the
impossibility of otherwise discovering the truth is not construed from
hence, that other witnesses were not actually concerned, but that, from
the nature of the crime, or from regard had to the place and time, other
witnesses could not be present." Many other passages from the same
authority, and from others to a similar