This phrase is used to respond when one person says something you disbelieve, and then another person comes in to support them. The point is that a lie doesn't become more true simply because another person (of similar sketchiness) tries to back it up.
A: No way man, I wasn't even there that day, you can even ask Jimmy, he'll tell you I wasn't there.
B: Jimmy? Oh, awesome, now Jimmy's backing up your story. Well, just goes to show, "one lies and the other swears to it."
5👍 1👎