Sorry for the delay, Mondays are always busy at my office. Additionally, I've been doing some online research to better answer your questions. As to that....
I found a case with some similar facts. It is not identical to your friend's situation but it is close. The case is here, http://www.in.gov/judiciary/opinions/pdf/03100601ewn.pdf. As you can see from the case, that defendant had not yet been sentenced and he had a viable and new defense that came up prior to his sentencing.
At the same time, it does contain some language that might be helpful to your friend's situation. In that case, the court overruled the trial court, withdrew the plea and sent the case back to the trial court to begin anew.
As a note, here's the statutory language to which I've been referring and taken from the case in the link above:
Indiana Code Section 35-35-1-4(b) states the applicable standard when a defendant pleads guilty pursuant to an agreement with the State and then requests to withdraw the plea:
After entry of a plea of guilty . . . , but before imposition of sentence, the court may allow the defendant by motion to withdraw his plea . . . for any fair and just reason unless the state has been substantially prejudiced by reliance upon the defendant's plea. . . . The ruling of the court on the motion shall be reviewable on appeal only for an abuse of discretion. However, the court shall allow the defendant to withdraw his plea . . . whenever the defendant proves that withdrawal of the plea is necessary to correct a manifest injustice.
As you can see, it uses the "manifest injustice" language I mentioned earlier.
I also came across an article that discusses a case with some similarities to your friend's situation. The article can be found here, http://www.theindianalawyer.com/attorney-must-register-as-a-sex-offender/PARAMS/article/27284. In that case, the plea agreement specifically stated that the defendant would NOT need to register as a sexual offender. However, when accepting the plea, the judge informed the defendant that Indiana law requires him to register as an offender and sentenced him accordingly.
While I pointed out that the first case in this box provides some helpful language, I will reiterate what I have been stating all along, I believe that the odds of success for your friend are extremely low. He should proceed with an appeal if he desires, I would just caution him to do so with his eyes wide open.
Also, several customers have asked how they may direct a question to me in particular. If you specifically want me to assist you in your legal matter, just put "FOR JOSEPH" in the subject line and I will gladly pick up the question as soon as I am on-line.