in law a brief is a formal written argument submitted to a court. it is in a format required by that particular court system. in civil law a brief generally contains the legal arguments in a lawsuit. in a criminal procedure briefs involve the state prosecuting one or more defendants for breaking one or more laws. in general, briefs contain references to the statutes, legal precedents and arguments applied to the facts for this particular case. when an attorney writes a brief, they are implicitly promising to give the court good reasons for ruling in favor of their client.