To say something that we know to be false, with the intention of deceiving others, is always sinful since "It is a profanation of speech, whereas the purpose of speech is to communicate known truth to others" (Catechism 2485). Perjury, telling a lie under oath, is an especially serious sin, asking Almighty God to witness to something that is false. It may also involve the condemnation of the innocent. the increased punishment of the accused or the exoneration of the guilty. Calumny is where we say something false about another person which harms their reputation. Detraction is the sin of saying true things that detract from our neighbour's reputation without a proportionate reason or duty in justice to do so.
The gravity of a lie is measured by the truth that is deformed, the intention of the liar and the damage done by the lie. In some cases, a lie may only be a venial sin but that does not make it a "white lie" in the sense of something harmless.
Although we should not speak falsehood, we are not obliged to convey the truth to those who do not have a right to know. Professional confidences and personal information may legitimately be considered as private information, not to be divulged to others unless there is an overriding duty of justice. An example of such a duty would be the need to protect a child from harm.
In some cases, to tell the whole truth would be an offence against justice. For example, if a person asks where the local abortion clinic is. it would be Legitimate to make the equivocation: "I could not tell you." The person saying this does not wish to divulge the information because they do not want to cooperate in any way in the killing of an unborn child.
People can think up various situations in which it might seem right to tell a lie. In every case, however, we should either tell the truth or refuse to give information rather than abuse the gift of speech by lying.
What's your view? And do you have a dilemma of your own? Write to us at the address on this page or e-mail firstname.lastname@example.org