Eustace Winner is also a prosecutor. While he acts smarmy and confident, in reality he's been held up by his father his entire life. In this video, he will be voicing in Excelcius's breakdown, taking down his own father.

The only real voice sample is his OBJECTION line, which you can go off or you can be creative with the voice. He should sound almost like a whiny brat, but he also has confident moments especially in this scene.