Two items. One is about Will and the two criminal cases (related to Will).
I live in Illinois, Chicago actually, and have a "little" knowledge of the law. In the episode "Battle of the Proxies" (Season 4, Episode 10) towards the end, Will offers to help in the appeal process of man convicted in a down state county (Minooka). He says: "Our case is over. Our guy got convicted. Our duty's discharged." First, his "guy" can appeal and his duty could include the appeal and even if his firm isn't doing the appeal they have a duty to NOT give out anything (e.g. evidence, notes, etc), which can negatively affect his appeal. Should he actually share with anyone "stuff" his firm found out, which might negatively affect his (former) client's appeal, well, that is ground for action by the bar - and since he's already been suspended, I'd say this would be ground for disbarment, should he actually do it.
As for the appeals, they both have - IMHO - decent chance at appeal, as they can point to the case of the other person as to why they're not guilty. You'll note neither prosecution team tried to tie them together, but instead said each person acted alone. You'll notice it was the "People/State of Illinois," which convicted them both and even the state/people say they can't both be guilty. A joint appeal would be best, on this issue, with other points taken individually.
I'll also note Will said to Alica they were to vigorously defend their client, which is correct - thus his now back tracking seems out of place. What he might have done, though, was have Alica just not show up once they realized their client might be / was guilty.
Finally, to those who say this is just a show and the above stuff about Will is only for entertainment, I'll point out that Perry Mason had great excitement and the writers followed the law. "It is simply a lazy writer who doesn't take the time to be both factual and entertaining."