Let's say that you have a situation where most of what a given person tells you can safely be assumed to be Intentionally misleading. But mixed in with the lies, prevarications, etc., you also understand that some statements will be accurate. Of course, at the moment the statements are made, you have no way of discriminating.
How should you regard the accurate statements.
1. Assume that all statements are lies since even the true statements serve primarily to improve the "truthiness" of the lies. Put another way, if you can recognize at least some true statements as such, an average listener will, subliminally, give greater credulity to the lies.
2. You assume all statements are lies. Any you happen to recognize as true are just ignored - since in order to know that they are true, you had to have already been in possession of the relevant information.
I think that there are probably, at least a few more possible characterizations. So if you have one that might contribute to the discussion, let your wad fly.