How can anyone tell the difference between accidentally cached images and purposely cached images?
And how many people have child porn on their computer that they don’t know about?
That's precisely the point LJ. The cache is just part of your software's internal workings. If you visit a webpage, it caches all the pictures on that page. The cache means absolutely nothing unless there are thousands of pictures in it. You could easily load 50 to 100 just by visiting the wrong web page, following a malicious link, or a dozen other ways.
No one here on FR supports child porn. I'm certain of that. However, the more technically inclined understand this ruling, and why it's a good one. The image cache is simply not a reliable method to see if you were intentionally seeking child porn.
Now, I will grant you freely, the majority of unintentional child porn is apt to be acquired in the pursuit of legal porn, but as distasteful as that may be to some FReepers, seeking pictures of naked adult women isn't criminal.