Who is the guy advising Yoo?

Fmr. Deputy Asst. Attorney General Office of Legal Counsel John Yoo and Rep. Keith Ellison (D-MN) during House Judiciary Subcommittee Hearing on Detainee Interrogation torture, June 26, 2008
Yoo seen avoiding answering simple questions regarding how his interpretation of torture was implemented. I would be curious to know who is sitting behind him helping him out