In very limited circumstances, a court will entertain a motion to overturn a conviction, called a motion to vacate or motion to set aside conviction. Typically these are only granted where there has been an error of law at the previous trial, the discovery of new exonerating evidence or the discovery of misconduct by the state. States also may allow you to file a motion to vacate an old case if you have maintained a crime-free history for a significant period of time. In these cases, you must file a petition in court and participate in a hearing on the motion.
Draft a motion to vacate. Obtain a blank copy of the motion from the clerk of court's office in the applicable courthouse or online from the court system website in many jurisdictions. The motion will have slightly different names depending on the jurisdiction where you are filing. Enter the caption of your criminal case into the header of the motion. While motion forms vary, you will generally need to input the original case's procedural history -- where it was heard, by whom and the outcome. Enter the grounds for your request and the information you believe provides adequate grounds for the petition. Attach to the petition a transcript of the trial, which you can order from the court reporter's office. Be factual and concise, as any false statements in the petition constitute perjury.
File your motion with the county clerk's office where the court filed the conviction. There is typically no filing fee for a motion of this nature. You generally have a choice to request a hearing on the motion or allow the court to review and rule on the motion without the need for a hearing on the matter. Serve your motion to the prosecutor's office to provide them notice and time to prepare.
Appear at a hearing on your petition, if you requested a hearing, or await the court's determination if you have not requested a hearing. If you appear at the hearing on your petition, present your arguments to the court. The state will be present and allowed to contest your claims. If the court finds in your favor, it will, depending upon the jurisdiction, vacate the previous sentence or conviction, which will remove that conviction from your criminal record.