An inquisitorial system is a legal system where the court or a part of the court is actively involved in investigating the facts of the case, as opposed to an adversarial system where the role of the court is primarily that of an impartial referee between the prosecution and the defense. Inquisitorial systems are used primarily in countries with civil legal systems as opposed to common law systems. Countries using common law, including the United States, may use an inquisitorial system for summary hearings in the case of misdemeanors such as minor traffic violations. The distinction between an adversarial and inquisitorial system is theoretically unrelated to the distinction between a civil legal and common law system. Some legal scholars consider inquisitorial misleading, and prefer the word nonadversarial. The function is often vested in the office of the public procurator, as in Russia, China, Japan, Germany, and Scotland.
In an inquisitorial system, the trial judges (mostly plural in serious crimes) are inquisitors who actively participate in fact-finding public inquiry by questioning defense, prosecutors and witnesses. They could even order certain pieces of evidence to be examined if they find presentation by the defense or prosecution to be inadequate.
The inquisitorial system applies to questions of criminal procedure, not substantive law; that is, it determines how criminal inquiries and trials are conducted, not the kind of crimes for which one can be prosecuted or the sentences that they carry. It is most readily used in some civil legal systems. However, some jurists do not recognize this dichotomy and see procedure and substantive legal relationships as being interconnected and part of a theory of justice as applied differently in various legal cultures.
In an adversarial system, judges focus on the issues of law and procedure and act as a referee in the contest between the defense and the prosecutor. Juries decide matters of fact, and sometimes matters of the law. Neither judge nor jury can initiate an inquiry, and judges rarely ask witnesses questions directly during trial. In some American jurisdictions, it is common practice for jurors to submit questions to the court that they feel were not resolved in direct or cross-examination. After testimony and other evidence are presented and summarized in arguments, the jury will declare a verdict (literally: "the spoken truth") and in some jurisdictions the reasoning behind the verdict. However, the discussions among jurors cannot be made public except in extraordinary circumstances. Appeals on the basis of factual issues, such as sufficiency of the sum total of evidence that was properly admitted, are subject to a standard of review that is in most jurisdictions heavily deferential to the judgment of the fact-finder at trial, be that a judge or a jury. The failure of a prosecutor to disclose evidence to the defense, for example, or a violation of the defendant's constitutional rights (legal representation, right to remain silent, an open and public trial) can trigger a dismissal or re-trial. In some adversarial jurisdictions (e.g., the United States), a prosecutor cannot appeal a "not guilty" verdict (absent corruption or gross malfeasance by the court).
In adversarial systems, the defendant may plead "guilty" or "no contest" in exchange for reduced sentences, a practice known as plea bargaining, which is an extremely common practice in the United States. In theory, the defendant must allocute or "voice" his or her crimes in open court, and the judge must believe the defendant is telling the truth about his or her guilt. In an inquisitorial system, a mere confession of guilt would not be regarded as ground for a guilty verdict, and the prosecutor is required to provide evidence supporting a guilty verdict; however, this requirement is not unique to inquisitorial systems, as many or most adversarial systems impose a similar requirement under the name corpus delicti.
Until the development of the Medieval Inquisition in the 12th century, the legal systems used in medieval Europe generally relied on the adversarial system to determine whether someone should be tried and whether a person was guilty or innocent. Under this system, unless people were caught in the act of committing crimes, they could not be tried until they had been formally accused by their victim, the voluntary accusations of a sufficient number of witnesses, or by an inquest (an early form of grand jury) convened specifically for that purpose. A weakness of this system was that because it relied on the voluntary accusations of witnesses, and because the penalties for making a false accusation were severe, victims and would-be witnesses could be hesitant to actually make their accusations to the court, for fear of implicating themselves. Because of the difficulties in deciding cases, procedures such as trial by ordeal or combat were accepted.
Beginning in 1198, Pope Innocent III issued a series of decretals that reformed the ecclesiastical court system. Under the new processus per inquisitionem (inquisitional procedure) an ecclesiastical magistrate no longer required a formal accusation to summon and try a defendant. Instead, an ecclesiastical court could summon and interrogate witnesses of its own initiative, and if the (possibly secret) testimony of those witnesses accused a person of a crime, that person could then be summoned and tried. In 1215, the Fourth Council of the Lateran affirmed the use of the inquisitional system. The council also forbade clergy from conducting trials by ordeal or combat. As a result, in parts of continental Europe, the ecclesiastical courts operating under the inquisitional procedure became the dominant method by which disputes were adjudicated. In France, the parlements — lay courts — also employed inquisitorial proceedings.
In England, however, King Henry II had established separate secular courts during the 1160s. While the ecclesiastical courts of England, like those on the continent, adopted the inquisitional system, the secular common law courts continued to operate under the adversarial system. The adversarial principle that a person could not be tried until formally accused continued to apply for most criminal cases. In 1215 this principle became enshrined as article 38 of the Magna Carta: "No bailiff for the future shall, upon his own unsupported complaint, put anyone to his law, without credible witnesses brought for this purposes."
The first territory to wholly adapt the inquisitional system was the Holy Roman Empire. The new German legal process was introduced as part of the Wormser Reformation of 1498 and then the Constitutio Criminalis Bambergensis of 1507. The adoption of the Constitutio Criminalis Carolina (peinliche Gerichtsordnung of Charles V) in 1532 made inquisitional procedures empirical law. It was not until Napoleon introduced the code d'instruction criminelle of the French code of criminal procedure on November 16, 1808, that the classical procedures of inquisition were ended in all German territories.
In the development of modern legal institutions which occurred in the 19th century, for the most part jurisdictions did not only codify their private law and criminal law, but the rules of civil procedure were reviewed and codified as well. It was through this movement that the role of an inquisitorial system became enshrined in most European civilian legal systems. However, there exist significant differences of operating methods and procedures between 18th century ancien régime courts and 19th-century courts. In particular, limits on the powers of investigators were typically added, as well as increased rights of the defense.
It would be too much of a generalization to state that the civil law is purely inquisitorial and the common law adversarial. Indeed, the ancient Roman custom of arbitration has now been adapted in many common law jurisdictions to a more inquisitorial form. In some mixed civil law systems such as those in Scotland, Quebec, and Louisiana, while the substantive law is civil in nature and evolution, the procedural codes that have developed over the last several hundred years are based upon the English adversarial system.
The main feature of the inquisitorial system in criminal justice in France and other countries functioning along the same lines is the function of the examining or investigating judge (juge d'instruction). The examining judge conducts investigations into serious crimes or complex inquiries. As a member of the judiciary, he or she is independent and outside the province of the executive branch, and therefore separate from the Office of Public Prosecutions which is supervised by the Minister of Justice.
Despite high media attention and frequent TV portrayals, examining judges are actually active in only a small minority of cases. In 2005, there were 1.1 million criminal rulings in France, while only 33,000 new cases were investigated by judges. The vast majority of cases are therefore investigated directly by law enforcement agencies (police, gendarmerie) under the supervision of the Office of Public Prosecutions (procureurs).
Examining judges are used for serious crimes, e.g., murder and rape, and for crimes involving complexity, such as embezzlement, misuse of public funds, and corruption. The case may be brought before the examining judge either by the public prosecutor (procureur) or, more rarely, by the victim (who may compel an instruction even if the public prosecutor rules the charges to be insufficient).
The judge questions witnesses, interrogates suspects, and orders searches for other investigations. Their role is not to prosecute the accused, but to gather facts, and as such their duty is to look for any and all evidence (à charge et à décharge), incriminating or exculpatory. Both the prosecution and the defense may request the judge to act and may appeal the judge's decisions before an appellate court. The scope of the inquiry is limited by the mandate given by the prosecutor's office: the examining judge cannot open a criminal investigation sua sponte.
In the past the examining judge could order committal of the accused, this power being subject to appeal. However, this is no longer the case, and other judges have to approve a committal order.
If the examining judge decides there is a valid case against a suspect, the accused is sent for adversarial trial by jury. The examining judge does not sit on the trial court which tries the case and is in fact prohibited from sitting for future cases involving the same defendant. The case is tried before the court in a manner similar to that of adversarial courts: the prosecution (and on occasion a plaintiff) seeks the conviction of accused criminals, the defense attempts to rebut the prosecution claims, and the judge and jury draw their conclusions from the evidence presented at trial.
As a result of judicial investigation and defendants being able to have judicial proceedings dismissed on procedural grounds during the examining phase, cases where the evidence is weak tend not to reach the trial stage. Conversely, the guilty plea and plea bargaining were until recently unknown to French law, and now it only applies to crimes for which the prosecution seeks a sentence not exceeding one year imprisonment. Therefore, most cases go to trial, including cases where the prosecution is almost sure to gain a conviction, whereas, in countries such as the United States, these would be settled by plea bargain.
In administrative courts such as the Council of State, litigation proceedings are markedly more inquisitorial. Most of the procedure is conducted in writing; the plaintiff writes to the court, which asks explanations from the administration or public service concerned; when answered, the court may then ask further detail from the plaintiff, etc. When the case is sufficiently complete, the lawsuit opens in court; however, the parties are not even required to attend the court appearance. This method reflects the fact that administrative lawsuits are for the most part about matters of formal procedure and technicalities.
Certain administrative proceedings within some common law jurisdictions in the United States may be similar to their civil law counterparts but are conducted on a more inquisitorial model. For instance tribunals dealing with minor traffic violations at the New York City Traffic Violations Bureau are held before an adjudicator who also functions as a prosecutor. They question witnesses before rendering judgements and setting fines.
These types of tribunals or boards function as an expedited form of justice where the state agents conduct an initial investigation and the adjudicator's job is to confirm these preliminary findings through a simplified form of procedure that grants some basic amount of due process or fundamental justice in which the accused party has an opportunity to place his or her objections on the record.