The Catechism of the Catholic Church says...

III. OFFENSES AGAINST TRUTH

2475 Christ's disciples have "put on the new man, created after the likeness of God in true righteousness and holiness."²⁷⁴ By "putting away falsehood," they are to "put away all malice and all guile and insincerity and envy and all slander."²⁷⁵

2476 False witness and perjury. When it is made publicly, a statement contrary to the truth takes on a particular gravity. In court it becomes false witness.²⁷⁶ When it is under oath, it is perjury. Acts such as these contribute to condemnation of the innocent, exoneration of the guilty, or the increased punishment of the accused.²⁷⁷ They gravely compromise the exercise of justice and the fairness of judicial decisions.

2477 Respect for the reputation of persons forbids every attitude and word likely to cause them unjust injury.²⁷⁸ He becomes guilty:

- of rash judgment who, even tacitly, assumes as true, without sufficient foundation, the moral fault of a neighbor;

- of detraction who, without objectively valid reason, discloses another's faults and failings to persons who did not know them;²⁷⁹

- of calumny who, by remarks contrary to the truth, harms the reputation of others and gives occasion for false judgments concerning them.

2478 To avoid rash judgment, everyone should be careful to interpret insofar as possible his neighbor's thoughts, words, and deeds in a favorable way:

Every good Christian ought to be more ready to give a favorable interpretation to another's statement than to condemn it. But if he cannot do so, let him ask how the other understands it. And if the latter understands it badly, let the former correct him with love. If that does not suffice, let the Christian try all suitable ways to bring the other to a correct interpretation so that he may be saved.²⁸⁰