An attorney can file a motion to quash if he believes an aspect of legal proceedings was irregular. If the court grants the motion, it will invalidate the subject of the motion, such as an attempt to introduce evidence, issue a subpoena, or indict a person for a crime. Attorneys on all sides of a case can file such motions and must be prepared to argue them to the judge, as the judge wants to hear clear justifications for the motion. Filing a motion without good cause can be grounds for penalties from the court if the judge feels an attorney was attempting to delay the trial.
One very good reason for a motion to quash is a mistaken identification. A prosecutor might initiate charges against a defendant, only to learn that the identification was wrong because a witness was coached or made an innocent mistake. The prosecutor could file a motion to quash the charges, asking the court to nullify them and stop the proceedings. Likewise, if a subpoena or summons is related to a false identification, it is possible to file a motion to invalidate the court order.
In the case of evidence, a motion to quash usually asks the judge to suppress the evidence because of a problem with it. If the chain of evidence was broken, the court could suppress it on the grounds that it is questionable. Likewise, if it is confidential or highly prejudicial, a motion to quash will keep it out of the court. An attorney arguing a civil case concerning a patent matter, for instance, might ask that evidence containing proprietary information be suppressed because it could endanger her client. Evidence tampering would also be grounds for this type of motion.
Attorneys may believe that a court order or activity is invalid because it is in the wrong jurisdiction. They can file motions to stop the procedure, and the court will determine if the jurisdiction is appropriate. The emergence of new information can trigger a motion to quash as well, if the information suggests that a court order would be unjust or unreasonable, given the new circumstances.
The judge will review the information presented by the attorneys and consider legislation and case law when deciding whether to grant the motion. Each judge has a slightly different approach to the law, and attorneys must tailor their arguments to the judge for the best results. If an attorney believes a motion was wrongly granted or rejected, this can become an important topic at an appeal.