A motion to suppress is a request made in a criminal trial by the defendant, asking the judge to exclude evidence because it was gathered illegally or in violation of the defendant's constitutional rights, states Nolo. The judge decides whether or not to grant the motion.
The defense lawyer submits motions to suppress to the judge before the trial begins, according to Lawyers.com. Evidence most commonly attacked on constitutional grounds includes confessions, arrest and search warrants, and eyewitness identifications. Defendants must be read Miranda rights before police legally can gather a confession, for example, to preserve a defendant's right against self-incrimination. Miranda rights include the right to remain silent and the right to an attorney. Protection from unlawful search and seizure means that arrest and search warrants must be signed by a judge and be applied for based on probable cause, while eyewitness identifications must be made under careful and fair circumstances. The defense may file a motion to suppress if the defendant's rights were abridged in any of these situations. A defendant's full constitutional rights are based on both federal and state constitutions.