The Supreme Court of India, since its inception in 1950, has evolved significantly from a traditional appellate court to a powerful constitutional court, playing a pivotal role as the ultimate interpreter and guardian of the Constitution. This evolution has been marked by a dynamic interpretation of its powers, particularly through judicial review and public interest litigation.

Initial Jurisdiction (Post-1950): Upon its establishment, the Supreme Court was endowed with several jurisdictions:

1. Original Jurisdiction (Article 131): To hear disputes between the Union and states, or between states.
2. Appellate Jurisdiction (Articles 132-136): To hear appeals from High Courts in constitutional, civil, and criminal matters, and through special leave petitions.
3. Advisory Jurisdiction (Article 143): To provide advisory opinions to the President on questions of law or fact.
4. Writ Jurisdiction (Article 32): To enforce Fundamental Rights, allowing individuals to directly approach the SC for their violation.

Evolution and Expansion of Jurisdiction as a Constitutional Court:

1. Judicial Review: Although not explicitly mentioned in the Constitution, the Supreme Court firmly established its power of judicial review early on (e.g., A.K. Gopalan v. State of Madras, 1950). This power allows it to examine the constitutionality of legislative enactments and executive orders, ensuring they conform to the provisions of the Constitution. This is fundamental to its role as a constitutional court, upholding the supremacy of the Constitution.

2. Basic Structure Doctrine (Kesavananda Bharati v. State of Kerala, 1973): This landmark judgment was a watershed moment. The Court ruled that while Parliament has the power to amend the Constitution, it cannot alter its 'basic structure' or 'essential features'. This doctrine significantly enhanced the SC's role as the ultimate arbiter of constitutional amendments, placing a substantive limit on legislative power and safeguarding fundamental constitutional values, including many Fundamental Rights.

3. Public Interest Litigation (PIL) (1980s onwards): The advent of PIL revolutionized the Court's jurisdiction. By relaxing the traditional rule of 'locus standi' (that only an aggrieved party can approach the court), the SC allowed any public-spirited citizen or organization to file petitions on behalf of marginalized and vulnerable groups. This led to:

   • Expansion of Rights: PIL led to the recognition of new rights (e.g., right to clean environment, right to livelihood, right to education, right to health) as implicit within the broader ambit of Article 21 (Right to Life and Personal Liberty).
   • Judicial Activism: The Court became more proactive in addressing social and economic injustices, often issuing detailed directives to the executive and legislature, sometimes venturing into policy-making domains.

4. Expansion of Article 21 (Right to Life and Personal Liberty): The Supreme Court has given an expansive interpretation to Article 21, transforming it into a repository of various rights essential for a dignified human existence. This broad interpretation has allowed the Court to intervene in diverse areas, from environmental protection to prison reforms.

5. Role in Electoral Reforms: Through various judgments, the SC has issued directives to the Election Commission and the government, leading to significant electoral reforms, such as mandatory disclosure of assets and criminal antecedents by candidates.

6. Environmental Jurisprudence: The Court has played a crucial role in developing environmental law in India, issuing landmark judgments on pollution control, forest conservation, and sustainable development.

7. Upholding Judicial Independence: The SC has consistently asserted and protected the independence of the judiciary, notably through the 'Collegium System' for judicial appointments and transfers, ensuring the judiciary's autonomy from executive interference.

Conclusion: The Supreme Court of India's journey as a constitutional court has been dynamic and transformative. Through its robust exercise of judicial review, the pioneering Basic Structure Doctrine, and the innovative use of Public Interest Litigation, it has not only interpreted the Constitution but also actively shaped its evolution. This has cemented its position as a vital check on legislative and executive power, a protector of fundamental rights, and a crucial institution in upholding the rule of law and the democratic fabric of India.