Murder By The Book - Ender's Game

How does Donut know if Akumu is town?

Also, how is it certain that Akumu and I are not both town? There seems to be a lot of speculation about scum motives there. Solaris especially seems to have acted quite oddly and erratically through the game. Look at the Eberron Lynch, Akumu was almost certain of Eberron's guilt based on Solaris's choice to save him, yet donut suggests Eberron is in fact town. What do we actually know for certain about Solaris's logic?

Donut is a cop.