A Motion to Vacate/Set Aside Sentence (Motion Under 28 U.S.C. Sec. 2255) is a legal process in which a convicted person can challenge the legality of their sentence or conviction. These motions are typically used when a person believes that their conviction or sentence was unlawful due to some kind of error or violation of their rights. This type of motion is commonly used when a person believes that their sentence was imposed in violation of the Constitution or laws of the United States. The motion is filed in the court in which the defendant was convicted and can be filed at any time before the expiration of the sentence. The most common types of motions filed under 28 U.S.C. Sec. 2255 are motions for new trial, to reduce a sentence, or to have a sentence vacated or set aside. In order to be successful, the defendant must demonstrate that their conviction or sentence violated their rights or was imposed in violation of the Constitution or laws of the United States. If the court finds that the defendant's motion has merit, they may grant the motion and vacate or set aside the sentence.