How do you know when he's lying?

I have such a bad memory that it is easier for me to tell the truth and handle the consequences then trying to remember a lie later.Besides,one of my major pet peeves are liars.

his lips move LOL don't tell me us men have tells when it comes to lying. I may be doomed

I know my other half is lying because his mount is open! But seriously, it's really easy to tell if he is lying. He doesn't normally look me in the eye and he takes a little while to think about what he is going to say so sometimes he answers me too quickly so I know he had prepared a lie and other times he pretends to forget that I have spoken to him or gives a stupid answer like "not a lot" if I ask what he is doing and I will ask him a few times so then I know he has taken that time to think of a lie. Now, he seems to be trying to look at me when he is lying, probably because he thinks I will think he is telling the truth but I can just tell in his eyes when he is lying. I don't know what it is but there is just something that I see when he is lying to me and it's funny because I also see that he thinks I think he is telling the truth and expects me to believe him.