If someone answers a question in a way which doesn’t make sense in relation to the question being asked, do you think it means the person is lying?
I can’t really answer your question – you haven’t given me enough to go on.
You can often tell if someone isn’t telling the truth by their body language. We call them “tells” – gazing over your shoulder, scratching a nose or pulling at an ear, fidgeting or grimacing can let you know that they are fully aware they are not being honest. Changing the subject may indeed be a way of avoiding the issue.
But it’s also possible that the person you’re wondering about answered in a way you didn’t want, or answered in the way they felt truthful. If you’d like to tell me what was the question, and what was the answer, I may be able to make a better guess. Otherwise, you’ll have to trust your own instincts – and they can be reliable unless you’re hoping to hear one thing and upset you hear something else!