Fairness is difficult to put in the form of strict legal rules and principles that cover every situation. A system of rules so strict that even a few innocent people get unfairly punished A system not so strict that even a few guilty people go unfairly unpunished Due process of law holds that the second answer is more correct, for many reasons. On a practical level, there's less of a danger to the whole legal system. If your system is letting a few guilty slip through, chances are that those lucky evil-doers might change their ways, or in any case, law enforcement or informal methods of social control can pick up the slack. Essential and fundamental fairness refers to how important something is for maintaining democracy.
Legitimacy refers to how fairly the legal system is perceived.
Legality refers to how extensive the legal system is. With the exception of the ex post facto clause, the Constitution is mostly concerned with procedural due process, but for every fundamental freedom, there's a larger freedom involved. All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and the State wherein they reside. Well, I've said previously that I think the Fifth is more about substantive due process and the Fourteenth is more about procedural due process, but that's just my interpretation. The correct answer is it depends on your interpretation, and most importantly, your stance toward incorporation, how much of the Bill of Rights is covered by the Fourteenth Amendment.