Grossberg is very strict and tends to speak nostalgically of his past.  He has a habit of loudly and exaggeratedly clearing his throat to draw someone's attention.  He appears to be fond of his past employees even after years of seeing them.  In a sense, Grossberg represents an old generation of veteran lawyers who have perhaps lost sight of their trade's true purpose and become tainted with corruption.

I imagine Grossberg to have a lower pitched voice, or I can even see him with a higher pitched one, similar to Rabbit from Winnie the Pooh!  However, feel free to give him a voice you think would fit!