What is the primary function of Lokpal under Section 20 of the Lokpal and Lokayuktas Act, 2013?

In Mohd. Yunus Khan v. State of U.P., where the initiating disciplinary authority acted as a witness and imposed dismissal, the Supreme Court held that the action violated:

In which landmark case was it held that a violation of natural justice principles by State action leads to arbitrariness and consequently violates Article 14?