Lying isn’t one single behavior. It can be an outright fabrication (“That didn’t happen”), a partial truth (“Nothing happened” while omitting the key detail), or a distortion that changes the meaning of what occurred. People also mislead by omission—staying quiet when the truth would likely hurt their image.
For your question—why is he lying—motive is the hinge. Two people can both give inconsistent stories, yet one might be scared and trying to minimize damage, while the other might be managing perception. The difference affects what you should do: support and boundaries for fear-based lying, versus accountability and protective steps for intentional deception.
Experts in psychology and investigative interviewing commonly treat deception as a communication problem, not just a moral failing. That means you focus on patterns of credibility, context, and consequences—rather than trying to “catch” someone with a single tell.
