You've got some documents from a witness. You're looking at them. The documents themselves reveal that they're not privileged and/or that a statutory exception applies to the privilege. So you use them, since you know for certain that they're not, in fact, privileged.
But the other side keeps screaming at you that these documents are privileged. And they file a motion. Both to get back the documents and to disqualify you for using privileged documents.
No big deal, right? You know they're not privileged. So you attach the purportedly (but not) privileged documents, which are in your possession anyway, to your opposition, confident that you'll prevail.
Sorry. The Court of Appeal holds that the trial court isn't permitted to look at the documents to see if they are, in fact, privileged. Even if they're already in your possession. Even if the trial court has not ordered their production (which would, indeed, violate the Evidence Code). And unless you can prove that the documents are privileged without talking about what's in the document, you lose.
Oh, yeah. And you might be disqualified.
So holds the Court of Appeal.