on account of some fault of his, as in the case of
unbelievers and persons of evil repute, as well as those who are
guilty of a public crime and who are not allowed even to accuse;
sometimes, without any fault on his part, and this owing either to a
defect in the reason, as in the case of children, imbeciles and
women, or to personal feeling, as in the case of enemies, or persons
united by family or household ties, or again owing to some external
condition, as in the case of poor people, slaves, and those who are
under authority, concerning whom it is to be presumed that they might
easily be induced to give evidence against the truth.

Thus it is manifest that a person's evidence may be rejected either
with or without some fault of his.

Reply Obj. 1: If a person is disqualified from giving evidence this
is done as a precaution against false evidence rather than as a
punishment. Hence the argument does not prove.

Reply Obj. 2: Good is to be presumed of everyone unless the contrary
appear, provided this does not threaten injury to another: because,
in that case, one ought to be careful not to believe everyone
readily, according to 1 John 4:1: "Believe not every spirit."

Reply Obj. 3: To give evidence is necessary for salvation, provided
the witness be competent, and the order of justice observed. Hence
nothing hinders certain persons being excused from giving evidence,
if they be considered unfit according to law.
_______________________

FOURTH ARTICLE [II-II, Q. 70, Art. 4]

Whether It Is Always a Mortal Sin to Give False Evidence?

Objection 1: It would seem that it is not always a mortal sin to give
false evidence. For a person may happen to give false evidence,
through ignorance of fact. Now such ignorance excuses from mortal
sin. Therefore the giving of false evidence is not always a mortal
sin.

Obj. 2: Further, a lie that benefits someone and hurts no man is
officious, and this is not a mortal sin. Now sometimes a lie of this
kind occurs in false evidence, as when a person gives false evidence
in order to save a man from death, or from an unjust sentence which
threatens him through other false witnesses or a perverse judge.
Therefore in such cases it is not a mortal sin to give false evidence.

Obj. 3: Further, a witness is required to take an oath in order that
he may fear to commit a mortal sin of perjury. But this would not be
necessary, if it were already a mortal sin to give false evidence.
Th