The first use of the word "case" concerns the lawyer's role of representation.  "I took on three new cases today," says an attorney, meaning that the attorney opened three new "files."  These may be three new clients, or perhaps two new clients and a new "matter" for an existing client.  The word "case" in this sense frequently means an adversarial situation -- a dispute such as a divorce, a criminal prosecution, a medical malpractice claim -- or a seemingly non-adversarial matter that has the potential for becoming adversarial -- such as a will, an incorporation, or a property settlement. 

 Legal disputes generally fall into two categories, criminal and civil.  In the former, a governmental body represents the interests of the public at large against an individual accused of a crime.  In the latter, private or public parties oppose other private or public parties in non-criminal legal matters.  Approximately ninety percent or more of all legal disputes are resolved outside the formal legal arena of the courtroom, some before formal legal proceedings are filed in a court or administrative agency and some after such proceedings are filed.  Such resolutions are usually referred to as settlements in civil cases.  In criminal cases, such resolutions usually result in charges being "dropped" or a guilty plea being entered pursuant to a plea bargain. 

 Those legal disputes that do not "settle," or that settle only after some activity in a formal legal arena, lead to the second use of the word "case," meaning either a trial or hearing before an administrative agency or a court, or an appeal to a higher court.  "I've got three cases next week," says an attorney, meaning that the attorney has three trials or hearings set in various courts.  Those adversarial legal disputes that do not settle and are resolved in court lead to the third use of the word "case," meaning a written judicial opinion issued by a court.  "The Supreme Court handed down the Jones case yesterday."  The published opinions of appellate courts account for most of the pages in law school textbooks.  "I briefed four cases for tomorrow's class."