What is the difference between procedural due process and substantive due process?

Answer 1

substansive due process is the promise of the fundamental rights that are implicit in ordered society procedural due process is the promise of fundamental fairness in legal proceedings
In general, substantive due process prohibits the government from infringing on fundamental constitutional liberties. By contrast, procedural due process refers to the procedural limitations placed on the manner in which a law is administered, applied, or enforced. Thus, procedural due process prohibits the government from arbitrarily depriving individuals of legally protected interests without first giving them notice and the opportunity to be heard.

Answer 2

Procedural and substantive due process are two aspects of the constitutional concept of "due process" outlined in the Fifth and Fourteenth Amendments that (theoretically) guarantees a form of fairness through consistent use of constitutional and legal safeguards.

Many constitutional scholars contend that the Fifth Amendment was intended only to guarantee procedural due process, to place limits on the government's ability to deprive a person of "life, liberty, or property" without taking certain protective steps on behalf of the individual, as outlined in the Bill of Rights (more specifically the Fifth and Sixth Amendments). Examples include the right to a jury trial, right to confront witnesses against him (or her), protection against being tried for the same crime twice, protection against involuntary self-incrimination, right to the effective assistance of counsel, and so on.

Substantive due process, as expounded by 17th-century English jurist Sir Edward Coke, deals with liberty interests, or the right of people to live without unnecessary and arbitrary government interference.

In the United States, Congress exercised the concept of substantive due process in the Missouri Compromise of 1820, which abolished slavery in Federal Territories. The Missouri Compromise gave rise to the doctrine of "once free, always free," holding once a slave had lived in "free" territory, his (or her) liberty could not be revoked (he or she could not be re-enslaved). The Supreme Court temporarily squashed this notion in Dred Scott v. Sandford, (1857), when it held the Missouri Compromise unconstitutional and ruled slaves were property, not people with rights.

More recently, the Supreme Court has divided liberty (substantive) interests into two categories: the first are those expressly enumerated in the Constitution, such as the First Amendment freedom of speech and religion; the second involve fundamental liberties not specifically listed but still considered essential to living in a free and just society, such as the right to privacy, and more abstract concepts such as the right to personal autonomy (within certain parameters) and dignity.