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.

❌ Objection 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.

❌ Objection 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. Therefore the giving of false evidence is not always mortal sin.