In England and Wales (and other Commonwealth countries, e.g., Australia) the phrase refers to the papers given to a barrister when they are instructed.
To achieve these ends, the brief must appeal to the accepted forces such as statutory law or precedent, but may also include policy arguments and social statistics when appropriate.
Depending on local rules, the court may then decide the case purely based on the submitted briefs or may hear oral argument by the parties.
A brief contains a concise summary for the information of counsel of the case which the barrister has to plead, with all material facts in chronological order, and frequently such observations thereon as the solicitor may think fit to make, the names of witnesses, with the "proofs," that is, the nature of the evidence which each witness is ready to give, if called upon.
In the early part of the 19th century the possession of a brief-bag was strictly confined to those who had received one from a king's counsel (silk).
King's Counsel were then few in number, were considered officers of the court, and had a salary of £40 a year, with a supply of paper, pens and purple bags.
These bags they distributed among rising juniors of their acquaintance, whose bundles of briefs were getting inconveniently large to be carried in their hands.
The only brief-bag allowed to be placed on the desks is the red bag, which by English legal etiquette is given by a leading counsel to a junior as a reward for excellence in some important case.
In English ecclesiastical law a brief meant letters patent issued out of chancery to churchwardens or other officers for the collection of money for church purposes.
Such briefs were regulated by a statute of 1704, but are now obsolete, though they are still to be found named in one of the rubrics in the Communion service of the Book of Common Prayer.
In the rules of the United States Supreme Court and circuit courts of appeals the brief is required to contain a concise statement of the case, a specification of errors relied on, including the substance of evidence, the admission or rejection of which is to be reviewed, or any extract from a charge excepted to, and an argument exhibiting clearly the points of law or fact to be discussed.