ask him lots of questions about this, and see if he gets unconfortable?! haha, and stare into his eyes, when people lie they usually dont look right into your eyes. :P
You can confront him of lying, but you could say that I still wanna be friends even though you lied. And if you're wrong, say I'm sorry for doubting you, can we still be friends? If you have any other problems that you think I can suggest to or solve, I'm on mibba almost every day. =]