The blogger formerly known as Rainman posts here and here on the use of footnotes in legal writing.
Some time last year, a lawyer from Knoxville asked me why did I use footnotes as I had done in a particular brief and was a disciple of Bryan Garner.
The honest answer (as opposed to what I told her) was that I wanted the judge to know that they were there, but I didn't care too much whether he read them. I had not much experience with the judge, and so I cited a bunch of case law, more than necessary (but not more than usual). What I wanted him to be thinking about was at the top, but if he thought I was making it up (as he may have done), he could check the notes at the bottom. He read the brief and knew the case, of that I'm sure, but whether the footnotes made any difference I could not say.