when can i make a laydown like this??

[thedorf]

I think that whenever you say you KNOW something at the poker table you should mentally define your terms. Obviously KNOW in this case does not mean; if he flipped his cards over and I saw that I was beat I would still call. That would be idiotic and you would never ever do it. So you actually didn't KNOW you were beat according to this definition of "know".

I think you made a fine call and should make the same call every time a similar situation arises. There are circumstances where you could lay down aces on this river (you have to call two cold for example). But there's really no need to sweat these river calls for one bet heads up in big pots. Your problem (a financial one) will arise if you do decide to start folding in these situations.