Most law clerks are recent law school graduates who were at the very top of their class and graduated from the most prestigious law schools. Various studies have shown clerks to be influential in the formation of case law through their influence on judges' decisions. Working as a law clerk generally opens up career opportunities.
Because of the selection criteria, many notable legal figures, professors, and judges were law clerks before achieving greatness in other areas of the law.
Five Supreme Court Justices previously clerked for other Supreme Court Justices: Associate Justice Byron White clerked for Chief Justice Frederick M. Vinson, Associate Justice John Paul Stevens clerked for Associate Justice Wiley Rutledge, Associate Justice Stephen Breyer clerked for Associate Justice Arthur Goldberg, and Chief Justice John Roberts clerked for Chief Justice William Rehnquist (when Rehnquist was still an Associate Justice). Rehnquist himself had previously clerked for Associate Justice Robert H. Jackson.
Some judges seek to hire law clerks who not only have excelled academically but also share the judge's ideological orientation. However, this occurs mostly at the level of some state supreme courts and the United States Supreme Court. Law clerks can have a great deal of influence on the judges with whom they work.
Upon completing a judicial clerkship, a law clerk often becomes very marketable to elite law firms.
Almost all federal judges have at least one law clerk; many have two or more. Associate Justices of the U.S. Supreme Court have four clerks, and the Chief Justice has five. Generally, law clerks serve a term of one to two years, however some federal judges hire a permanent law clerk. Such judges usually have one permanent law clerk and one or two law clerks who serve on a term basis.
Far and away, the most prestigious clerkship--and most difficult to obtain--is one with a U.S. Supreme Court Justice; there are only 36 of these positions available every year. However, in recent times securing a federal court of appeals clerkship with a federal judge has been a prerequisite to clerking on the Supreme Court. The next most prestigious place to clerk is at one of the U.S. Court of Appeals, with the United States Court of Appeals for the District of Columbia typically being more desirous than the other Courts of Appeals. Further, clerkships with a Court of Appeals judge who frequently sends clerks on to the Supreme Court, often called feeder judges, (e.g., Alex Kozinski, James Harvie Wilkinson III, Merrick Garland) are especially difficult to obtain. Generally, the third most sought after clerkship is one with a trial level federal court judge, such as a United States District Court judge or United States Tax Court judge (or in some cases, like New York or Texas, a State Supreme Court judge); like the Court of Appeals, some U.S. District Courts are more sought after than others (e.g., Northern District of California, Southern District of New York) due to the district's popular location. There are also federal clerkships with lower level trial court judges, like United States District Court Magistrate judges, who are supervised by United States District Court judges, United States Tax Court Special Trial judges, who are supervised by United States Tax Court judges, or United States Bankruptcy Court judges, whose cases are appealable to United States District Court.
Former federal law clerks are generally highly sought by large firms. Firms believe that such individuals have excellent legal research and writing skills, and a strong command of the Federal Rules of Civil Procedure and Federal Rules of Criminal Procedure. Firms are even more interested in a former law clerk if the firm generally appears before the clerk's former judge. Clerks who served with specialty judges, such as a United States Bankruptcy Court judge, are often pursued by firms both for the reasons that other clerks are hired, and because they have training in a highly complex and specialized area of the law. As such, many former United States Bankruptcy Court clerks end up working in the bankruptcy or business reorganization departments of large firms. The interest in former law clerks is seen by the fact that most large firms have a special hiring process for former clerks, and often pay such individuals large signing bonuses.
Generally interested candidates apply for Federal Clerkships roughly a year before the clerkship begins, meaning that law students formally apply early in the fall of their third year. The federal clerkship application process has also largely been streamlined by the National Federal Judges Law Clerk Hiring Plan, and the OSCAR system, an online database in which federal judges post upcoming vacancies (although not all federal judges use this system). The National Federal Judges Law Clerk Hiring Plan sets dates for when federal judges may receive application, and when they may contact, interview, and hire law clerks. Generally the applications may be looked at early in the fall (in 2007 it was Tuesday, September, 4) with contact and interviews happening a few weeks later. These dates only apply to the hiring of matriculating third-year law students; practicing attorneys may apply earlier. The Supreme Court does not follow this timetable.
As a result of the extreme competition—both by the judges to get the best candidates and by candidates to get the best clerkships—the pace of the hiring is extremely quick. It is not unknown for federal judges to offer a candidate a clerkship at the conclusion of a first interview, and require that the candidate provide an immediate answer. Such job offers have come to be known as "exploding offers." Some have likened the process to land runs or feeding frenzies. While a few federal clerkships come available after September, most federal judges complete their hiring before the end of October.
Instead, California has largely switched to using permanent staff attorneys at all levels of the judiciary; a few judges do use law clerks, but they are quite rare. For example, the Supreme Court of California has over 85 staff attorneys, of whom about half are attached to particular justices and the rest are shared as a central staff. The California system has been heavily criticized for denying young attorneys the chance to gain experience, and low turnover has resulted in a lack of ethnic and gender diversity among the staff attorneys. But most California judges prefer staff attorneys because it avoids the problem of having to bring new law clerks up to speed on pending complex cases, particularly those involving the death penalty.
Students of law who, after law school, have passed the first of two required examinations join the Referendariat, a time of two years consisting of a series of clerkships: for a civil law judge, a criminal law judge or a prosecutor, a government office and finally at a law firm. However, these clerkships are primarily a part of the legal education, and the extent to which Referendare are a real help for their judges very much depend on their qualification.
In federal appeal courts (see Judiciary of Germany and the office of the Federal Prosecutor General, the duties of law clerks are performed by wissenschaftliche Mitarbeiter (German for "scientific assistant"). With few exceptions, they are lower court judges or civil servants, assigned for a period of three years to the respective Federal Court, and their clerkships serve as a qualification for a higher judgeship. However, some justices of the Federal Constitutional Court (who have the right to select their wissenschaftliche Mitarbeiter personally) prefer clerks from outside the courts or the civil service, especially those who are or were professors of law and who often hire people from academia (sometimes even young law professors). The clerks of the Federal Constitutional Court are deemed very influential and are therefore dubbed the (unofficial) Dritter Senat ("Third Senate") as opposed to the two official "senates" of 8 justices each which form the court.
In Mexico duties conferred to law clerks in some common law countries are charged in a person called "Secretario de Acuerdos", for lower courts and, "Secretario de Estudio y Cuenta" for higher court: "Suprema Corte de Justicia de la Nación". Secretario de Acuerdo's main activities are: conduct the public hearings, writing veredicts, order to execute sentences, and providing general assistance to Judges.
The ratio is about one law clerk per judge, and the clerk switch judge after a time, usually three months. The rationale being that working for different judges broadens the scope of learning.
The term as law clerk is two years, after which the law clerk may opt to apply to the Court of Appeals in the Administrative system or the General system ("kammarrätt" or "hovrätt") and continue on the path that traditionally leads to Judge, or leave the Court system for another career. Having completed the two years is considered qualifying and may open up career opportunities otherwise closed.
The work as a law clerk mainly entails assisting the judges with writing verdicts and decisions, keeping the records during trials and conducting legal inquirys. After about six months the law clerk is trusted with deciding simpler non-disputed issues by himself (such as registering prenuptials or granting adoptions). After about a year the law clerk is entrusted with judging simpler criminal and civil law cases by himself (in General Courts), such as petty theft or a civil case involving low sums of money.