Philip,
I think you have confused the cast of characters. The captain's name was DuBois, the left-seat copilot was Robert and the right-seat copilot was Bonin.
When the captain left the flight deck to take his rest, Robert had just returned from his rest. The captain did not unambiguously assign crew responsibilities in his absence. For example, although Robert occupied the LHS, the captain did not explicitly designate him PIC.
What do you mean by "cp"?