Fundamental procedural legal safeguards of which every citizen has an absolute right when a state or court purports to take a decision that could affect any right of that citizen (such as, re USA, Fifth Amendment).
The most basic right protected under the due process doctrine is the right to be given notice and an opportunity to be heard (audi alteram partem), and the right to an impartial judge (nemo judex in parte sua).
The term is now also in use in other countries, again to refer to basic fundamental legal rights such as the right to be heard.
The term originated in England, but has taken on much importance in the United States of America as encompassing initially basic procedural rights, and since enlarged to include substantial rights, and is set out in §1 of the Fourteenth Amendment.
Due process first appeared as a term in law in an English statute of 1354 and in reference, generally, to the Magna Carta of 1215, which stated:
"No free man shall be taken or imprisoned or disseized or exiled or in any way destroyed, nor will we go upon him nor send upon him, except by the lawful judgment of his peers or by the law of the land."
It was Edward III (pictured) who signed the statutes which entrenched the concept into the common law; first, the 1354 Liberty of Subject Act (28 Edward 3):
"No man of what estate or condition that he be, shall be put out of land or tenement, nor taken, nor imprisoned, nor disinherited, nor put to death, without being brought in answer by due process of the law.”
Fourteen years later, the Observance of Due Process of Law Act (42 Edward 3):
"At the request of the Commons by their petitions put forth in this Parliament, to eschew the mischiefs and damages done to divers of his Commons by false accusers, which often times have made their accusations more for revenge and singular benefit than for the profit of the King, or of his people, which accused persons, some have been taken and caused to come before the King’s council by writ, and otherwise upon grievous pain against the law, it is assented and accorded, for the good governance of the Commons, that no man be put to answer without presentment before justices or matter of record or by due process and writ original, according to the old law of the land; and if any thing from henceforth be done to the contrary, it shall be void in the law, and holden for error.”
The drafters of the American Constitution referred to due process; that the government must use due process of law in any process which might deprive a person of life liberty or property.
The growth of due process as grounds for ever more sophisticated legal rights was steady.
In 1897, the courts ruled that due process meant that the government had to justly compensate any person from whom they expropriated property.
In 1932 (Powell v Alabama 287 US 45) and 1963 (Gideon v Wainwright 372 US 335 (1963)), the requirements that the government had to provide legal counsel for indigent defendants, then any defendant facing a felony, and, finally, any defendant facing a jail sentence, were all eventually read-in to the requirement for due process.
In Powell v Alabama, Justice Sutherland wrote:
"Let us suppose the extreme case of a prisoner charged with a capital offence, who is deaf and dumb, illiterate and feeble minded, unable to employ counsel, with the whole power of the state arrayed against him, prosecuted by counsel for the state without assignment of counsel for his defense, tried, convicted and sentenced to death. Such a result, which, if carried into execution, would be little short of judicial murder, it cannot be doubted would be a gross violation of the guarantee of due process of law; and we venture to think that no appellate court, state or federal, would hesitate so to decide.
"The duty of the trial court to appoint counsel under such circumstances is clear, as it is clear under circumstances such as are disclosed by the record here; and its power to do so, even in the absence of a statute, can not be questioned."
Writing his own opinion but following the majority decision, Justice Clark of the US Supreme Court, in Gideon v Wainwright, wrote:
"... the Constitution makes no distinction between capital and noncapital cases. The Fourteenth Amendment requires due process of law for the deprival of "liberty" just as for deprival of "life," and there cannot constitutionally be a difference in the quality of the process based merely upon a supposed difference in the sanction involved."
Similar in many regards to what other common law jurisdictions refer to as administrative law or rules of natural justice, due process has also come to mean that the government, before making any decision which might deprive a citizen of liberty or property, must give notice of the Government's case, afford to the citizen an opportunity of being heard and thus to accommodate a hearing even, in some cases, a trial before an impartial arbitrator.
In Pennoyer v Neff 95 US 733 (1878), the US Supreme Court said of due process:
"Whatever difficulty may be experienced in giving to those terms a definition which will embrace every permissible exertion of power affecting private rights, and exclude such as is forbidden, there can be no doubt of their meaning when applied to judicial proceedings. They then mean a course of legal proceedings according to those rules and principles which have been established in our systems of jurisprudence for the protection and enforcement of private rights. To give such proceedings any validity, there must be a tribunal competent by its constitution that is, by the law of its creation - to pass upon the subject-matter of the suit; and, if that involves merely a determination of the personal liability of the defendant, he must be brought within its jurisdiction by service of process within the State, or his voluntary appearance."
Due process has also come to mean that statutes must be precise.
If the government is going to restrict activity, it must be clear about what activity is being restricted.
A US statute that is vague can be struck down under the due process requirements of the American Constitution.