Re: Punishment for this?
I would keep him by my side for 3 days (that's about all I could handle, lol). Tell him that since he can't tell the truth, you have to keep a SUPER close eye on him to make sure he's not going to do something and lie about it.
And honestly, I'd have a serious sit down talk with him. Explain to him that it hurts you. Cry if you need to. Tell him that you REALLY want to be able to believe him when he tells you something. Tell him that you don't want you guys' relationship to suffer because he lies to you. Explain that while he thinks he might be in DEEP trouble for doing something, the punishment won't really be all that bad if he just tells the truth to begin with. He's 8. He understands. I do this with my 6 year old and he RARELY lies. It really seems to snap him back into reality. He knows that if he lies to me, I won't trust him, and all privileges go out the window.