This is a difficult question to answer, if he pled guilty he would have 1 year to challenge the plea via habeas corpus if it was a misdemeanor, and 4 years from the date of the plea to challenge it if it was a felony. If he was convicted of a crime he would have to timely file the appropriate appellate documents. Without knowing the dates, the crimes or reading the transcripts it would be hard to make a determination based on the facts presented.
The answer to your question depends on the types of crimes he was charged with, and when.
James L. Yeargan, Jr. is licensed to practice law in the State of Georgia. All information given is based only on Georgia law, and is not directly applicable to any other jurisdictions, states, or districts. Any answer given assumes the person who asked the question holds a Georgia Drivers License, and this license is not a commercial drivers license (CDL). This response, or any response, is not legal advice. This response, or any response, does not create an attorney/client relationship. The response is in the form of legal education and is intended to provide general information. Any state specific concerns should be directed to an attorney who is licensed to practice law in that respective state.
All of this is dependent upon the charge and when he was sentenced and numerous other questions. Contact a lawyer and bring all the paperwork to discuss the issue and see what can be done. There will be a fee involved, but it may give you some piece of mind to know that you have an opportunity to file something or you don't.