Words sometimes sound wrong

Sometimes, I find a person lying, but I don’t have any direct proof to catch. Sometimes, I have evidence, but I don’t want to make relations bad, so I don’t want to show them that I know they are lying. But when I found these people were blaming me for their own fault to me, then? I had to speak up… but if I do so, others will make a wrong impression on me. Well, then I have nothing to do, whatever I said, that was the truth.