The two prevalent legal systems in the world are the Adversarial system (Accusatorial or the Common law system) and the Inquisitorial system (Continental or the Civil law system).
In a common law system, an adversarial approach is used to investigate and adjudicate guilt or innocence. The adversarial system assumes that truth is most likely to result from the open competition between the prosecution and the defence. Primary responsibility for the presentation of evidence and legal arguments lies with the opposing parties, not with a judge. Each side, acting in its self-interest, is expected to present facts and interpretations of the law in a way most favorable to its interests. The approach presumes that the accused is innocent, and the burden of proving guilt rests with the prosecution. Through counterargument and cross-examination, each side is expected to test the truthfulness, relevancy, and sufficiency of the opponent's evidence and arguments.
The adversarial system places decision-making authority in the hands of neutral decision makers. The judge ascertains the applicable law and the jury determines the facts. The system emphasizes procedural rules designed to ensure that the contest between the parties is a fair fight. Critics of the adversarial approach argue that the pursuit of winning often overshadows the search for truth. Furthermore, inequalities between the parties in resources and in the abilities of the attorneys may distort the outcome of the adversarial contest.
The inquisitorial process is characterized by a continuing investigation conducted initially by police and then more extensively by an impartial examining magistrate. This system assumes that an accurate verdict is most likely to arise from a careful and exhaustive investigation. The examining magistrate serves as the lead investigator—an inquisitor who directs the fact-gathering process by questioning witnesses, interrogating the suspect, and collecting other evidence. The attorneys for the prosecution (the accuser) and defence (the accused) play a limited role in offering legal arguments and interpretations that they believe the court should give to the facts that are discovered. All parties, including the accused, are expected (but not required) to cooperate in the investigation by answering the magistrate's questions and supplying relevant evidence.
The case proceeds to trial only after completion of the examining phase and the resolution of factual uncertainties, and only if the examining magistrate determines that there is sufficient evidence of guilt. Under the inquisitorial approach, the trial is merely the public finale of the ongoing investigation. At this point, the accused assumes the burden of refuting the prima facie (apparent) case of guilt developed in the examining phase. Critics argue that the inquisitorial system places too much unchecked power in the examining magistrate and judge, who both investigate and adjudicate (legally determine) the case.
The Bhutanese legal system is based on the adversarial principle of procedure with some elements of the inquisitorial system. The courts take no sides and the judges are umpires of the litigants. The judges allow uninterrupted hearing to the litigants or their jabmis. They are given opportunity to make presentation to the Court and answer questions posed by the judges. The plaintiff and the defendant or their jabmis can submit evidence to substantiate their legal contentions and the courts decide cases based on the facts and issues submitted by the parties.
Thus, onus propandi or the burden to proof beyond reasonable doubt lies on the prosecutor in a criminal case and on the plaintiff to prove his case by a Fair Preponderance of the Credible Evidence in a civil action.
The adversarial principle is well enshrined in the Bardo Thoedrel (Book of the Dead - Garun Puran), which is performed on the third day of the Tshechu every year all over the country and dates back to the 8th century. Here the guilty pleads, invoking the doctrine of necessity and extenuating circumstance. He also pleads the ignorance of law and fact before the Shinjey Chhoekigyap.
Similarly, the prosecutor (Dre Nagchung) invokes the doctrine of actus reus and mens rea and submits that the accused is guilty of mass destruction of wild life and the environment. He submits that the accused has used slanderous words, injured and killed many innocent animals, assaulted the poor and innocent people, has condemned the saints and their religion, burnt down the shrines and temples, polluted the ocean and injured marine life. Besides, he has tormented his parents and demolished many stupas. The prosecutor submits his evidence of the various names like the Red-Handed Murderer, Negelbum the sinner, the Black Low Caste Murderer, and the Black killer that various people were calling the accused. Thus, the prosecutor (Dre Nagchung) proves before the Chhoekigyap that the accused is a ruthless sinner.
The king of Purgatory pronounces judgment based on the facts and issues submitted by the Prosecutor and the defence jabmi. Therefore, it is similar to the common law system.