This is where an archiving product would save your butt... Legal discovery is a pain aint' it?!
That said, depending on what version of BE, you may be able to at least restore emails based on the user using GRT, or via Recovery Storage Groups. But you still have to sift through it manually to narrow down the amount of "static," you'll have to go through.
Alternatively, you should get a good archiving product, and it would have paid for itself right about now...