Stuck my head in on the Jackie Murphree civil trial a second ago and finally figured out what this guy is doing. It appears he works for one of the defendants and is in charge of the two video screens that hover above the courtroom. (It's kind of like Jerry World, but different).
But this guy just waits for a particular cue from a lawyer and the he's throwing up pictures and video clips instantaneously. He's quick and good at it.
I've never seen a guy in a courtroom dedicated to that one purpose.