In essence, what does 'Due Process of Law' mean?

Answer: A. 'Due Process of Law' essentially means the principle of NATURAL JUSTICE. Due Process of Law is a constitutional doctrine of American origin (5th and 14th Amendments to the US Constitution) requiring that both the SUBSTANCE (the law itself must be just, fair and reasonable) AND the PROCEDURE (it must be followed fairly) meet standards of natural justice. Indian courts post-Maneka Gandhi v Union of India (1978) effectively imported Due Process into the interpretation of Article 21 ('procedure established by law'). Due Process embodies the twin pillars of natural justice: (a) audi alteram partem (hear the other side) and (b) nemo judex in causa sua (no one can be judge in their own cause). Distractors: (B) 'Procedure established by law' is the literal Indian doctrine (post-A.K. Gopalan, narrower than due process). (C) 'Fair application of law' is broader but vague. (D) 'Equality before law' is Article 14 — overlapping but distinct concept. Source: syllabus Indian Constitution at Work Ch 2 (Rights) / Maneka Gandhi judgment.