Okay, basically the trial comes down to two options...
Option 1 - Don't go to the rebel base for evidence. Ignore it. Pretend it never existed. Interview the two witnesses, get the to offer up their information, talk to the guy and get him to admit he was having an affair, and then go to trial.
In addition to the two key admissions (that Gluupo planted the medal and that Firith Me testifies that Elassa was a Dark Jedi) you want to emphasize 2 things whenever you can:
1) No one saw the murder take place.
2) The affair between Elassa and Sunry was finished.
Also, make sure to bring up the affair as soon as you can, before the Sith can. Otherwise, Sunry will be an idiot and lie. That's bad.
Remember, the judges are neutral - don't run your mouth off about how Sith are evil, and don't play up the fact that the guy was a war hero or a cripple, or that Elissa was a spy. Bringing up those facts will hurt you more than they help. Stick to the basics and you should win.
Option 2 - The Sith base is a red herring - there's no evidence there at all. There is relevant information in the Republic base, on the computers there, which is pretty damning. If you see this, confront Sunry about it, and defend him anyway, you shift to the dark side. If you see it and plead guilty, he gets executed, and that's also bad. It's a lose/lose situation.
The best result here is to play dumb, as silly as that sounds.