Speak with a local criminal defense attorney who does post conviction work with plea agreements. This question is very fact specific. Very much a frying pan or fire type question. You can't appeal a plea agreement, you technically made a knowing, intelligent, a voluntary waiver of your rights. But, there is a motion that may be filed. Talk with a knowledgeable, skilled, experienced post-conviction attorney in the jurisdiction of the conviction.
The attorney from California is correct. The case can be re-opened on a successful motion, but you must be careful what you wish for, because if the plea agreement is vacated, the case ultimately can end up worse than the deal you made.
In this case, it sounds like there is little downside to trying since he received such a stiff sentence after a plea. Feel free to have your friend contact our office.
Best of luck.
A defendant can take back their guilty plea before sentence is imposed if that guilty plea was not knowing and voluntary. However, after being sentence the defendant will have to file a PCR or Post Conviction Relief application, which requires that there was some error in the proceedings. The chances of reopening the case after sentencing, without any knew evidence, is not good.
Your friend can make a motion to withdraw his plea but these are hard to win, especially given all the questions that judges usually asked. Perhaps there is a claim of ineffective assistance of counsel. As for an appeal, that depends on whether your friend waived his right to appeal as part of the plea and what events took place before the plea that might be subject to an appeal such as a suppression hearing. I am a former federal and State prosecutor (Queens A.D.A.) and now handle criminal defense, including appeals so please feel free to check out my web site and contact me if your friend wishes to retain counsel.
Regardless of whether he waived his right to appeal, I suggest your friend instruct his attorney to file a notice of appeal without delay since time is of the essence. This will preserve his right to appeal. I further suggest that your friend consult with an experienced post conviction/appellate attorney about the feasibility and advisabilityter, your friend of challenging his conviction and/or sentence on appeal or by motion to vacate.