It is at US Constitution...

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Note added at 22 mins (2011-02-23 01:47:09 GMT)
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...and before at Carta Magna, UK:
The phrase due process of law first appeared in a statutory rendition of Magna Carta in A.D. 1354 during the reign of Edward III of England, as follows: "No man of what state or condition he be, shall be put out of his lands or tenements nor taken, nor disinherited, nor put to death, without he be brought to answer by due process of law."
http://en.wikipedia.org/wiki/Due_process

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Note added at 24 mins (2011-02-23 01:48:55 GMT)
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The constitutional guarantee of due process of law, found in the Fifth and Fourteenth Amendments to the U.S. Constitution, prohibits all levels of government from arbitrarily or unfairly depriving individuals of their basic constitutional rights to life, liberty, and property. The due process clause of the Fifth Amendment, ratified in 1791, asserts that no person shall "be deprived of life, liberty, or property, without due process of law." This amendment restricts the powers of the federal government and applies only to actions by it. The Due Process Clause of the Fourteenth Amendment, ratified in 1868, declares,"[N]or shall any State deprive any person of life, liberty, or property, without due process of law" (§ 1). This clause limits the powers of the states, rather than those of the federal government.

The Due Process Clause of the Fourteenth Amendment has also been interpreted by the U.S. Supreme Court in the twentieth century to incorporate protections of the Bill of Rights, so that those protections apply to the states as well as to the federal government. Thus, the Due Process Clause serves as the means whereby the Bill of Rights has become binding on state governments as well as on the federal government.

The concept of due process originated in English Common Law. The rule that individuals shall not be deprived of life, liberty, or property without notice and an opportunity to defend themselves predates written constitutions and was widely accepted in England. The Magna Charta, an agreement signed in 1215 that defined the rights of English subjects against the king, is an early example of a constitutional guarantee of due process. That document includes a clause that declares, "No free man shall be seized, or imprisoned … except by the lawful judgment of his peers, or by the law of the land" (ch. 39). This concept of the law of the land was later transformed into the phrase "due process of law." By the seventeenth century, England's North American colonies were using the phrase "due process of law" in their statutes.
http://legal-dictionary.thefreedictionary.com/Due Process of...