Doesn't RAID5 just distribute stripes of the data over the disks plus parity? I think they'd get random stripes of your data. If your stripe size is 128kb, they'd get a 128k chunk of an image here, a part of another image there... Text doesn't use a lot of space so there might be a long text or several emails within some stripe... If you're lucky that was just your spamfolder... If they're lucky, it's the text document containing your master password list plus your confession to all the crimes committed... Chances are they seize the disk with that specific data on it. Or maybe they happen to take one of the other ones. Could be on any of them.
Larger files get distributed over the disks due to striping. Depends on the file type... Maybe parts of large file can be used against you, maybe they can't.