The adversarial system or adversary system is a legal system used in the common law countries where two advocates represent their parties' case or position before an impartial person or group of people, usually a judge or jury, who attempt to determine the truth and pass judgment accordingly. It is in contrast to the inquisitorial system used in some civil law systems (i.e. those deriving from Roman law or the Napoleonic code) where a judge investigates the case. The adversarial system is the two-sided structure under which criminal trial courts operate, putting the prosecution against the defense. Basic features Adversarial systems are considered to have three basic features. The first is a neutral decision-maker such as a judge or jury. The second is presentation of evidence in support of each party's case, usually by lawyers. The third is a highly structured procedure. The rules of evidence are developed based upon the system of objections of adversaries and on what basis it may tend to prejudice the trier of fact which may be the judge or the jury. In a way the rules of evidence can function to give a judge limited inquisitorial powers as the judge may exclude evidence he or she believes is not trustworthy, or irrelevant to the legal issue at hand. Peter Murphy in his Practical Guide to Evidence recounts an instructive example. A frustrated judge in an English (adversarial) court finally asked a barrister after witnesses had produced conflicting accounts, "Am I never to hear the truth?" "No, my lord, merely the evidence", replied counsel. Parties Judges in an adversarial system are impartial in ensuring the fair play of due process, or fundamental justice. Such judges decide, often when called upon by counsel rather than of their own motion, what evidence is to be admitted when there is a dispute; though in some common law jurisdictions judges play more of a role in deciding what evidence to admit into the record or reject. At worst, abusing judicial discretion would actually pave the way to a biased decision, rendering obsolete the judicial process in question—rule of law being illicitly subordinated by rule of man under such discriminating circumstances. Lord Devlin in The Judge said: "It can also be argued that two prejudiced searchers starting from opposite ends of the field will between them be less likely to miss anything than the impartial searcher starting at the middle."