it is very difficult to "undo" a plea. seek out an appellate attorney or a seasoned criminal trial attorney who is familiar with the court that this plea took place in. The sooner this is done, the better. The attorney can advise you about the various grounds for withdrawing a plea in your state, but generally, you have to show that the plea was not voluntary or there was some important procedural error, or that the evidence would not have supported a guilty finding. These days most courts engage the defendant in a thorough examination which is called a colloquy wherein the judge asks the defendant a lot of questions to determine whether they are in fact pleading voluntarily. The attorney will have to get the records of the case and a transcript of that plea hearing. Be prepared for a significant financial cost.
Please consult with your own lawyer before following any opinions I am expressing here. If you do not have a lawyer on a criminal case, you better get one. You should not be looking for free advice as a substitute for having your own qualified advocate working with you on the case.
If your son is still within thirty days of the date on which he was sentenced on his plea he can file a motion for leave to withdraw the plea. It is up to the judge whether or not to allow the motion. The mere fact that he now regrets his decision is not adequate grounds and presumably he was already aware of the contents of the report when he entered the plea. The judge could easily deny his motion based on what you have posted. If he files a timely motion for leave to withdraw the plea and his motion is denied, then he can appeal the denial and ask the appellate court to allow him to withdraw his plea. The appeal will take a year or two. If he has missed the thirty day deadline, his only option is probably going to be the long shot of a post-conviction petition.
If leave to withdraw the plea is allowed, either by the trial judge or by the appellate court, your son will be back to square one facing the original charge without benefit of his plea, and he could get a considerably stiffer sentence if he is ultimately convicted. I encourage him to be very careful about this idea and to consult an attorney before he does anything he may come to regret even more than the plea that he regrets now.
He must file a motion to withdraw the plea within 30 days of the date on which the sentence was imposed. He must assert a legal basis to be allowed to withdraw the plea (possibly a conflict on the part of the PD?). A change of heart is insufficient. www.galivanlaw.net