The Difference Between Forbidden Deception and Euphemisms in Speech

Question:
When is speech considered deception and when is it considered a euphemism? How do we distinguish between deception in speech and euphemisms?

Answer:
Euphemisms are permissible if they are for a legitimate reason. For example, if someone asks, "Did you see so-and-so today?" and the speaker fears for the person's safety, he may say, "I did not see him," meaning he did not see him in that specific place, or in his house, or in the other person's house, out of concern for his safety.
As for deceptions that lead to consuming what is forbidden or dropping a right, that is deception itself. For instance, if someone takes a hundred riyals from another person by robbery or theft, and then swears an oath before the judge saying, "You did not take anything from him," interpreting his statement to mean he did not take anything from him today or yesterday, such an interpretation is of no benefit.