It is a litigation trick to have your paralegals sit behind you during a trial and have them nod in agreement with your expert witness. So they seem like regular onlookers who are being convinced by the expert. The idea is that the jury, or judge, sees this while the testimony is being given and reacts with the natural human instinct to belong and gives more credence to what your expert is saying.
Such was the sad scene yesterday in court during the Robert Wone trial. Paralegals and assistants left and right sat behind the attorneys in the gallery and nodded their heads as defense witnesses testified. It's a bit of a cheesy trick, but it must be effective for the attorneys in the past if they are using it here.